Population December 2003

BULLETIN
Vol. 58, No. 4 A publication of the Population Reference Bureau

Population: A Lively
Introduction, 4th Edition
by Joseph A. McFalls Jr.

Our fascination with

population stems from an
interest in our own lives.

Change is a
fundamental aspect
of any population.

Demographic forces
have a profound
impact on society.
Ne
w
Ed
iti
on
Population Reference Bureau (PRB)
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Trustees
Patty Perkins Andringa, Consultant and Facilitator, Bethesda, Maryland
Suzanne M. Bianchi, Professor of Sociology and Director of the Population Research Center, University of
Maryland, College Park
Bert T. Edwards, Executive Director, Office of Historical Trust Accounting, Office of the Secretary, U.S.
Department of the Interior, Washington, D.C.
James H. Johnson Jr., William Rand Kenan Jr. Distinguished Professor and Director, Urban Investment
Strategies Center, University of North Carolina, Chapel Hill
Terry D. Peigh, Executive Vice President and Director of Corporate Operations, Foote, Cone & Belding,
Chicago, Illinois
Francis L. Price, Chairman and CEO, Q3 Industries and Interact Performance Systems, Columbus, Ohio
Douglas Richardson, Executive Director, Association of American Geographers, Washington, D.C.
Gary B. Schermerhorn, Managing Director of Technology, Goldman, Sachs & Company, New York
Barbara Boyle Torrey, Independent Writer and Consultant, Washington, D.C.
Leela Visaria, Professor, Gujarat Institute of Development Research, Ahmedabad, India
Montague Yudelman, Senior Fellow, World Wildlife Fund, Washington, D.C.

Mildred Marcy, Chairwoman Emerita

Population December 2003

Vol. 58, No. 4

BULLETIN A publication of the Population Reference Bureau

Population: A Lively
Introduction, 4th Edition
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Fertility. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Box 1. The Intermediate Variables That Affect Fertility . . . . . . . . . . . . . . . . . . 5
Box 2. Fertility Measures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Figure 1. U.S. Birth Rates by Age of Mother, Selected Age Groups,
1955–2002 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Figure 2. Age Patterns of Fertility: Japan, Mali, and the United States, 2001 . . . 9 Page 3
Mortality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Figure 3. U.S. Death Rates by Age for Males, 1900 and 2001 . . . . . . . . . . . . . 10
Figure 4. Life Expectancy at Selected Ages for Males and Females,
Japan, 2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Table 1. The 15 Major Causes of Death: United States, 2001 . . . . . . . . . . . . . 13
Migration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Table 2. U.S. Population in 2000 by Residence in 1995 . . . . . . . . . . . . . . . . . 15
Figure 5. People Who Moved Last Year, by Age: United States, 2001 . . . . . . . 16
Population Size and Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Box 3. The Demographic Balancing Equation . . . . . . . . . . . . . . . . . . . . . . . . . 20
Box 4. Where Do Demographic Data Come From?. . . . . . . . . . . . . . . . . . . . . 21
Box 5. Households and Families . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Page 17
Population Composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Figure 6. Population Pyramids: Mali, United States, and Italy, 2000 . . . . . . . 24
Figure 7. Germany’s Population by Age and Sex, 1996 . . . . . . . . . . . . . . . . . . 27
Figure 8. Population of the United Arab Emirates, by Age and Sex, 2000 . . 28
Population Distribution. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Figure 9. Changing Distribution of World Population, 1950, 2003,
and 2050 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Population Growth Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Figure 10. World Population Growth Through History . . . . . . . . . . . . . . . . . . 33
Figure 11. The Classic Stages of Demographic Transition. . . . . . . . . . . . . . . . 34
Page 26

Continued on page 2
1
 Concern About Population . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Suggested Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

About the Author

Joseph A. McFalls Jr., a demographer and sociologist, is a professor at Villanova University.
McFalls received a Ph.D. in demography from the University of Pennsylvania and an MBA
from the Harvard Business School. His research interests center on population fecundity and
the demography of the U.S. black population. He is the author or co-author of numerous arti-
cles and books, including Sociology, Disease and Fertility, Psychopathology and Subfe-
cundity, and Social Problems.
The author wishes to acknowledge the extensive and expert editorial assistance of Mary
Kent and contributions made by other PRB staff members. Ann Riley provided valuable com-
ments on the earlier edition.

© 2003 by the Population Reference Bureau

2
Population: A Lively
Introduction
by Joseph A. McFalls Jr.

M
ost people think demography
is just math in disguise—a
sort of dry social accounting.
Once exposed to the subject, many
change their minds. They come to
appreciate the profound impact
demographic forces have on societies.
This has never been more true than
during the past half-century, a period Photo removed for copyright reasons.
in which the United States and other
societies have experienced unprece-
dented social and demographic
change. Since these demographic
forces have not been stilled, they will
continue to cause social change and
to shape social programs for the bal-
ance of our lives and beyond.
People also find demography fasci- The study of population delves into personally relevant
topics for individuals and societies all over the world.
nating because it deals with so many
personally relevant topics. Nearly all
the major events of people’s lives have
demographic implications: birth, Will you move around the block or
schooling, marriage, choosing an overseas?
occupation, childbearing, retirement, • How long will you live? What are
and death. Consider the following the chances of your dying within a
questions: year? Within 10 years? What is
• When and where were you born? likely to kill you?
How many others were born the These are all in part demographic
same year? questions. Indeed, if people are not
• What is your probability of getting interested in demographic phenom-
married or divorced? ena, they are not interested in them-
• Do you have children or do you selves.
ever plan to? How many, and how Demography, or population stud-
far apart? ies, is a discipline, an “interdisci-
• What kind of job will you have? pline,” and a subdiscipline. It is
How often will you change jobs? clearly a discipline because it is a
What are your chances of promo- field with its own body of interre-
tion? When will you retire? lated concepts, techniques, journals,
• How many times will you move? departments, and professional associ-
3
 ations. Demography is also an inter- issues and problems associated with
disciplinary field because it draws its population growth.
subject matter and methods from
many disciplines, including sociol-
ogy, economics, biology, geography,
history, and the health sciences.
Fertility
Finally, demography is also consid- The study of population dynamics
ered a subdiscipline within some of must begin with fertility. Fertility
these same major disciplines. In most refers to the number of births that
universities, demography courses are occur to an individual or in a popula-
taught within the sociology curricu- tion. In 2003, fertility rates of national
lum, perhaps because population populations ranged from an average
phenomena have so long been of 1.1 children per woman in the for-
linked to social processes.1 mer Soviet republics of Georgia and
Demography is defined as the Ukraine to 8.0 children per woman in
The study of study of human populations: their the West African country of Niger.
population size, composition, and distribution, as The average for the United States was
well as the causes and consequences 2.0, and for the world, 2.8. In 2003,
dynamics must of changes in these characteristics. more than 4 million babies were born
begin with Populations are never static. They in the United States and about 27 mil-
grow or decline through the interplay lion in India. Worldwide, 136 million
fertility. of three demographic processes: human beings were born, or 258
birth, death, and migration. If some babies per minute.
groups within a population grow or Fertility must be distinguished from
decline faster than others, the compo- its sister term, fecundity, which refers
sition of the whole is altered. to the physiological ability of individu-
This Population Bulletin presents als or couples to have children. Some
the basic what, why, and how of the individuals are infecund—unable to
study of demography. It is not a com- bear children because of disease or
prehensive treatment of the subject, genetic dysfunction. Mothers who are
but it does provide an overview of breastfeeding their babies often are
demographic processes and the basic temporarily infecund because of nat-
measures used to assess them. In addi- ural hormones released by their bod-
tion, it traces population trends in the ies. There is documented evidence of
world and the United States, surveys women giving birth to 30 or more chil-
the demographic differences among dren (usually including twins, triplets,
population groups, and examines and other multiple births).2 Thus, for
broad social issues linked to popula- individuals, fecundity probably ranges
tion change. from zero to about 30 children.
The first three sections of this Bul- The maximum fecundity of a
letin provide the framework for study- population, which is composed of
ing the dynamics of population. individuals with varying levels of
Fertility, mortality, and migration are fecundity, is thought to be about 15
at the root of all demographic children per woman.3 This is the the-
change. The fourth section reveals oretical maximum number of chil-
how changes in fertility, mortality, and dren a population of women could
migration affect a population’s size produce if they engaged in regular
and growth rate, and how population sexual intercourse from menarche, at
projections are calculated. The fifth around age 12, until they reached
section delves into the composition of menopause, at around age 50, and
population according to common never used any form of birth control.
variables: age, sex, and race or ethnic- The theoretical maximum of 15
ity. The sixth section describes how children is a far cry from real-life levels.
the geographic distribution of popu- Even in the world’s highest-fertility
lation changes, primarily through countries, the average has rarely
migration. The final sections discuss exceeded eight children per woman.
4
What accounts for this large gap? In Ukraine achieved one of the lowest
every society a variety of cultural, eco- fertility rates on record for a nation—
nomic, and health factors interfere 1.1 births per woman—largely
with the process of human reproduc- because of relatively high rates of con-
tion. These factors include cultural val- traceptive use and abortion.5
ues regarding childbearing (does the Where contraceptive use and abor-
society value large or small families?); tion are rarely used, the postpartum
social roles (is the wife primarily a infecundity and marriage determinants
childbearer and childrearer?); eco- are more important. The Hutterites, a
nomic realities (do parents rely on chil- North American religious sect, aver-
dren to look after them in old age?); aged 12 children per woman in the
and the prevalence of diseases such as 1930s—the highest fertility on record
gonorrhea that impair fecundity. for any population—by promoting
Cultural and economic factors do early and universal marriage and
not affect fertility directly; they influ- eschewing contraception and abortion.
ence another set of variables that The importance of the intermedi-
determine the rate and level of child- ate variables differs around the world
bearing. In 1956, demographers because of cultural practices and
Kingsley Davis and Judith Blake iso- beliefs that affect people’s behavior.
lated the factors that control the In many African countries today,
probability that a woman of reproduc- women marry young and rarely use
tive age (roughly ages 15 to 49) will contraceptives, yet fertility is kept to a
produce a child. These intermediate six-child average through cultural fac-
fertility variables affected a society’s
fertility level through their impact on
fecundity, sexual unions (including Box 1
marriage), or birth control (see Box The Intermediate Variables That Affect Fertility
1). The factors operate in every soci-
ety, but the relative importance of Fecundity
each varies tremendously. • ability to have intercourse
In the 1980s, demographer John • ability to conceive
Bongaarts demonstrated that four of • ability to carry a pregnancy to term
these variables explain nearly all the
variation in fertility levels among popu- Sexual Unions*
lations. These “proximate determi- • the formation and dissolution of unions
nants of fertility,” as he termed them, • age at first intercourse
could be quantified and expressed as a • proportion of women who are married or in a union
simple formula, creating a versatile • time spent outside a union (separated, divorced, or
method for statistical analysis. The widowed, for example)
four proximate determinants are: (1) • frequency of intercourse
the proportion of women married or • sexual abstinence (religious or cultural customs, for
in a sexual union, (2) the percent of example)
women using contraception, (3) the • temporary separations (military service, for example)
proportion of women who are infe-
cund (because they are breastfeeding, Birth Control
for example), and (4) the level of • use of contraceptives
induced abortion.4 • contraceptive sterilization
These proximate determinants • induced abortion
have a direct biological effect on fer-
tility. The importance of each *Includes marriage as well as long-term and casual relationships.

depends on social, economic, and

References
health factors within a population.
Kingsley Davis and Judith Blake, “Social Structure and Fertility: An
Contraceptive use and abortion are
Analytic Framework,” Economic Development and Cultural Change 4, no. 3
the key proximate determinants of (April 1956); and Joseph A. McFalls Jr. and Marguerite McFalls, Disease
fertility levels in the United States and and Fertility (New York: Academic Press, 1984).
most developed countries. In 2003,
5
 tors. In accordance with ancient tradi- Measuring Fertility
tions and beliefs, women in many The national fertility rates discussed
African societies breastfeed their above are total fertility rates (TFRs).
babies until age 2 or 3, thus prolong- The TFR is commonly used because it
ing the infecund period following is easy to visualize what it stands for:
childbirth (postpartum amenorrhea). the average total number of children a
In some African societies, mothers are woman will have. But the TFR is a syn-
expected to abstain from sex for up thetic rate; it does not measure the fer-
to two years after childbirth, espe- tility of any real group of women.
cially while they are breastfeeding. The TFR measures the fertility of
Polygamy, or having more than one an imaginary group of women who
wife at the same time, is another cul- pass through their fictitious reproduc-
tural practice that affects fertility. tive lives subject to the rates of child-
Some African men have more than bearing experienced by real women
one wife, and husbands often work in a given year. Although the TFR
away from home for months at a concept is not intuitively obvious, it is
time, further reducing the time their straightforward and easy to calculate
wives are, in demographers’ terms, from age-specific birth rates (see Box
“exposed to the risk of pregnancy.” 2). The TFR is a valuable measure for

Box 2
Fertility Measures
Demographers use a variety of Calculating the U.S. Total death, as shown in Table 1,
rates, ratios, and other statistics to Fertility Rate (TFR) for 2001 page 13.
measure fertility within a country Age-specific birth rates are
(2)
or for a population group. They Births to (3) also used to calculate the total
often refine these measures to (1) women in Age-specific fertility rate (TFR), one of the
Number of age group birth rate
examine the levels and trends Age of women 2001 (column 2 most valuable rates for com-
within a specific group—teenagers women (thousands) (thousands) column 1) paring fertility among coun-
or college-educated women, for *
tries and tracking changes over
15-19 9,844 454 0.046
example—or to reduce the effect time. The TFR is often cited as
20-24 9,619 1,022 0.106
of different age structures on the a measure of the average num-
25-29 9,333 1,058 0.113
crude birth rate. ber of children in a family, but
30-34 10,261 943 0.092
Most refined fertility measures this definition is not really cor-
35-39 11,138 452 0.041
zero in on women of childbearing rect. The TFR is a “synthetic”
40-44 11,477 93 0.008
age (usually ages 15 to 49). The measure that does not apply to
45-49 10,544 5 z
general fertility rate, for example, any specific woman or group
Sum 0.407
tracks the number of births per of women. The U.S. TFR for
1,000 women ages 15 to 49 (or TFR= Sum x 5 2.03 2001 (2.03), for example, mea-
*
sometimes ages 15 to 44). Rates Includes 7,781 births to women under age 15. sures the average number of
z = Less than 0.001.
are refined even more to measure Note: Rates may vary from published figures for 2001.
children American women
the number of births to women in Sources: B.E. Hamilton, P.D. Sutton, and S.J.
would have, assuming that, at
a smaller age group. Teen birth Ventura, National Vital Statistics Reports 51, no. 12 every age, they have children
rates generally refer to women (2003): table I; and B.E. Hamilton, J.A. Martin, at the same rate as women did
ages 15 to 19, and may be dis- and P.D. Sutton, National Vital Statistics Reports 51, in 2001. The TFR is the sum of
no. 11 (2003): table 1.
sected further to refer to teens 16 the rates for each five-year age
to 17 or ages 18 to 19. group multiplied by five, as
Demographers use similar techniques to examine illustrated in the table above.
other variables. Age-specific rates may be calculated
for deaths, migration, marriage, college attendance, References
and other social phenomena. Similarly, rates may be John R. Weeks, Population: An Introduction to Concepts and
calculated separately for individuals with specific Issues, 8th ed. (Belmont, CA: Wadsworth/Thompson Learn-
characteristics, such as birth rates for married ing, 2002): 193-99; and Arthur Haupt and Thomas T. Kane,
women, or death rates for white teenagers. Death Population Handbook: International Edition, 4th ed. (Washing-
rates may be calculated separately for each cause of ton, DC: Population Reference Bureau, 1998).

6
gauging fertility trends or comparing sures the number of daughters born
different populations. to a woman given current birth rates
Another attraction of the TFR is and her chances of living to the end
that it allows us to explore the concept of her childbearing years.6 These and
of replacement-level fertility. This is other refined rates allow demogra-
the level of childbearing at which cou- phers to compare the fertility of differ-
ples have an average of two children— ent countries more accurately.
just replacing themselves in the
population. A population with replace- Lifetime Fertility: Cohort Rates
ment-level fertility eventually will stop What if we want to measure the fertility
growing (as discussed in the section on of a certain group of women, for exam-
population growth). Actually, replace- ple, women born between 1940 and
ment-level fertility requires a TFR 1945? For women who are past their
slightly above 2.0, primarily because reproductive years, say above age 50, a
some children will die before they completed fertility rate can be esti-
grow up to have their own two chil- mated from the average number of The crude birth
dren. In a country with low mortality, children they bore from the time they rate is highly
such as the United States, a TFR of 2.1 experienced menarche in their early
produces replacement-level fertility. In teens until they reached menopause in sensitive to
a high-mortality country such as Sierra their 40s or 50s. population age
Leone, replacement-level fertility Completed fertility is a useful mea-
would require a TFR greater than 3. sure for comparing the fertility levels of structure.
The crude birth rate is the most different generations. In the United
easily obtained and most often States, women born between 1906 and
reported fertility measure. It is calcu- 1910 (the 1906-1910 birth cohort) pro-
lated from the number of babies born duced what was then the smallest num-
in a given year (or any other time ber of children per family in U.S.
period) divided by the mid-year popu- history, an average of 2.2 children per
lation, and it is expressed as the num- woman. Women from the 1931-1935
ber of births per 1,000 people. In cohort, who became parents during
2003, the estimated crude birth rate the baby boom, produced the century’s
was 14 births per 1,000 in the United highest fertility—a completed fertility
States and 22 births per 1,000 for the rate of 3.2 children per woman. Baby
world. National crude birth rates boomers—Americans born between
ranged from 8 in Bulgaria and 1946 and 1964—will probably average
Ukraine to 55 in Niger. fewer children than the 1906-1910
As the name implies, this rate is an cohort, but we will have to wait to find
imprecise measure of a society’s child- out until about 2010, when they have
bearing patterns. The crude birth rate completed their childbearing years.
is highly sensitive to the age structure Completed fertility is a cohort mea-
of a population. The crucial factor is sure because it describes the fertility
the percentage of young women in of a specific cohort of women. The
the reproductive ages, because these TFR and crude birth rate are period
women produce most of the babies. rates because they measure fertility for
Thus, a population with a relatively a given period of time. Cohort rates
high proportion of young people will tell us nothing about current fertility.
have a higher crude birth rate than a Likewise, period rates, such as the
population with a large proportion of TFR, cannot predict future fertility.
older people. The difference between cohort and
More refined rates attempt to mini- period rates explains how it is possible
mize the effects of age structure. In that, during the height of the U.S.
addition to the TFR, these include the baby boom (1957), the TFR reached
general fertility rate, which measures 3.7 children per woman, yet no cohort
the number of births per woman of of women born in the 20th century
childbearing age (ages 15 to 49), and has recorded a completed fertility rate
the net reproduction rate, which mea- of more than 3.2 children.
7
Figure 1 no children at all. Nineteen percent
U.S. Birth Rates by Age of Mother, Selected Age of women who were ages 40 to 44 in
Groups, 1955–2002 2001 had never had children, and
most of these women never will.8
Births per 1,000 women
250

Ages 20-24
Fertility Differentials
The overall fertility rate in the United
200 States has remained fairly stable since
the late 1970s, but American women
Ages 25-29
vary considerably in when and how
150 many children they have. Among all
women ages 15 to 44 in 2000, only 22
percent conformed to the two-child
100 average; 43 percent had not yet had
Ages 30-34 children, and 17 percent had three or
Ages 15-19 more children. What accounts for these
50 differences? The most predictable and
Ages 34-39 obvious fertility differential is age, but
Ages 40-44 income, race, religion, and many other
0 social, economic, and cultural factors
1955 1960 1965 1970 1975 1980 1985 1990 1995 2000
also influence childbearing.
Sources: B.E. Hamilton, P.D. Sutton, and S.J. Ventura, National Vital Statistics Reports 51,
no. 12 (2003): table 1; B.E. Hamilton, J.A. Martin, and P.D. Sutton, National Vital Statis- Age
tics Reports 51, no. 11 (2003): table 1; and National Center for Health Statistics, “Live Biotechnology and medical advances
Births by Age of Mother and Race, United States, 1933-1998” (www.cdc.gov/nchs/
data/natality/mage33tr.pdf, accessed Aug. 26, 2003).
are expanding the ages at which women
can have children. But few women give
birth before age 15 or after age 50. Over
U.S. Fertility this roughly 35-year span, birth rates
American women averaged more than vary substantially by age (see Figure 1).
seven children each until the early The postponement of childbearing
decades of the 19th century. Average is portrayed by the steep drop in the
fertility declined gradually thereafter, birth rate for women ages 20 to 24
interrupted only by the baby boom fol- during the 1960s and the 1970s. After
lowing World War II. The TFR reached 1975, the rate leveled off for women in
an all-time low of 1.74 children per their 20s, while it rose for women ages
woman in 1976, and then crept up to 30 to 34. Many of these older mothers
2.08 by 1990. Between 1990 and 2001, were having the children they had
the TFR varied between 1.97 and 2.08. postponed earlier in life. Despite con-
The baby bust of the 1970s came siderable media attention about
about in large part because of delayed increases in the number of women
marriage, widespread contraceptive becoming mothers in their 40s, the
use, and abortion. Judging by the birth rate for women ages 40 to 44 is
long-term fertility trend and the cur- lower in 2002 than it was in the 1960s.
rent social trends favoring low fertil- Finally, Figure 1 reveals that teen
ity—including postponement of birth rates remained relatively low in the
marriage and childbearing to older 1970s and 1980s, despite large increases
ages, high divorce rates, and the large in the proportion of teenagers who
proportion of women in the labor were sexually active. The teenage birth
force—we are not likely to see U.S. rate edged up around 1990, but
birth rates rise very far.7 increases in contraceptive use and a lev-
Although most American women eling of the share of teens who are sexu-
say they expect to have at least two ally active helped lower the teen birth
children, many women have delayed rate to its lowest level ever by 2002.9
marriage and childbearing so long Birth rates by the age of the mother
that they will have only one child or follow the same general pattern in most
8
societies regardless of the level of fertil- Figure 2
ity: Rates are low in the teens, peak in Age Patterns of Fertility: Japan, Mali, and the
the 20s, and decline thereafter. But United States, 2001
comparisons of the age-specific rates in Births per 1,000 women
different countries reveal significant 300
variations, as shown in Figure 2. The
peak does not begin until the late 20s Mali
in Japan, where childbearing is highly 250 6.8 child average
concentrated in the late 20s and early
30s. In the United States, birth rates
200
are high for women throughout their
20s and into their early 30s. In the
West African country of Mali, where 150
the TFR was an estimated 6.8 in 2003, United States
birth rates also peak in the early 20s 2.0 child average
and then decline slowly, but childbear- 100
ing is less concentrated among young
women. Women ages 20 to 29 account 50
for about 40 percent of all births in Japan
Mali, compared with more than 50 1.3 child average
percent of births in the United States 0
and Japan. Malian women have higher 15–19 20–24 25–29 30–34 35–39 40–44 45–49
birth rates than American and Japan- Age of women
ese women at every age. Sources: B.E. Hamilton, J.A. Martin, and P.D. Sutton, National Vital Statistics Reports 51,
no. 11 (2003): table 1; Japan National Institute of Population and Social Security
Research, Latest Demographic Statistics 2003 (2003): table 4-7; and ORC Macro, Mali
Race and Ethnicity Enquête Démographique et de Santé (2003): table 4-1.
In many countries, racial and ethnic
minorities have higher fertility than
the majority. Often these differences Arabs in Israel and Asians in Russia
arise from religious beliefs and cul- are other examples of minority ethnic
tural traditions. Immigrants often or religious groups whose fertility
maintain the childbearing patterns of remains higher than the average for
their homelands when they arrive, but the country. But minorities do not
they and their children tend to incor- always have above-average fertility. In
porate the fertility patterns of their Malaysia, for example, the ethnic Chi-
adopted country over time. Hispanics nese minority has lower fertility than
born in the United States have lower the indigenous Malay population. In
fertility than U.S. Hispanics who were the United States, Japanese Americans
born abroad, for example. Likewise, and Chinese Americans have the lowest
fertility differences among European fertility of any major ethnic group.12
ethnic groups in the United States
(including Irish, German, and Italian Socioeconomic Status
American) have greatly diminished.10 In nearly every contemporary society,
A minority group’s fertility differ- the poor have more children than the
ences also are linked to its socioeco- rich. This also holds true for the United
nomic status. The fertility of African States within all major racial and ethnic
Americans has always been higher than groups. Income is closely related to
the rates for non-Hispanic white Ameri- educational attainment, which is often
cans, although the gap has narrowed in easier to measure. Individuals who have
recent years. This persistent difference completed more schooling tend to have
likely reflects African Americans’ lower higher-paying jobs. In general, fertility
socioeconomic status relative to whites. declines as the income and educational
In 2001, the TFR was 1.8 for non-His- attainment of women increase. In 2000,
panic white women and for Asian and for example, American women ages 35
Pacific Islander women, 2.1 for black to 44 with a graduate or professional
women, and 2.7 for Hispanic women.11 degree had an average of 1.4 children,
9
Figure 3 million, producing a U.S. crude death
U.S. Death Rates by Age for Males, 1900 and 2001 rate of 8.5 deaths per 1,000 people.
Deaths per 1,000 males An estimated 55 million people
300 died throughout the world that same
year. With a 2003 global population of
250
6.3 billion, these deaths produced a
death rate of 8.7 per 1,000. World-
1900 wide, death rates ranged from only
200
about 2 in Kuwait and the United
Arab Emirates to 28 in Mozambique.
150 The death rate measures the pro-
portion of a population that dies each
100 year, but comparing death rates
among populations does not show
2001
50 whether one population is healthier
or lives longer than another. The
0
death rate is strongly influenced by
Under 1 1–4 5–14 15–24 25–34 35–44 45–54 55–64 65–74 75–84 85+ the age structure of the population.
Death rates often are higher in more
Sources: E. Arias and B.L. Smith, National Vital Statistics Reports 51, no. 5 (2003): table developed countries such as Sweden
1; and U.S. Census Bureau, Sixteenth Census of the United States: 1940, Vital Statistics Rates
in the United States, 1900–1940 (1943): table 5. than in less developed countries such
as Nicaragua, even though more
developed countries tend to have
compared with 1.9 children for women healthier environments and better
with just a high school diploma and 2.5 medical services. A large proportion
children for women without a high of the population of more developed
school diploma.13 countries is in the older ages—the
ages at which most deaths occur—
Other Differentials while a relatively small proportion of
Numerous other social, religious, and the population of less developed
cultural factors are associated with countries is in the older ages. In 2003,
fertility differences. Most of these can only 3 percent of Nicaraguans were
be explained by age, income, or edu- age 65 or older, while 17 percent of
cational differences among these Swedes were age 65 or older.
groups. In just about every culture, When death rates are plotted by
women who work outside the home age on a graph, they form the charac-
have fewer children than those who teristic J-shaped curve of mortality
do not, and rural women have more (see Figure 3). The J pattern is found
children than urbanites. People who in all societies, but it is most pro-
actively practice a religion tend to nounced where mortality is high, as it
have higher fertility than nonreli- was in the United States in 1900. The
gious people. In the United States, death rates for U.S. males were
Catholics traditionally had more chil- higher in 1900 than they are today in
dren than Protestants, but this differ- many less developed countries.
ence has largely disappeared.14 The death rate is relatively high
during an infant’s vulnerable first
year of life, then it declines through-
out childhood and early adolescence
Mortality before starting an inexorable climb to
Mortality, the counterpoint to fertility, a towering peak after age 85. From
is the second cause of population the point of view of the mythical
change. The death rate for a popula- Grim Reaper, Americans are most elu-
tion is usually expressed as the num- sive at ages 10 and 11 when only one
ber of deaths per 1,000 people in a out of every 5,000 people dies, and
given year. In 2003, 2.5 million Ameri- most vulnerable at age 122 when vir-
cans died out of a population of 291.5 tually everyone is harvested.
10
Life Expectancy Figure 4
To better gauge the life chances of Life Expectancy at Selected Ages for Males and
individuals in a population and to Females, Japan, 2001
better compare mortality conditions
Additional years of life
among countries, we must look at the
average life expectancy. Both biologi- 84.9 Males Females
cal and social factors influence how 78.1
long individuals live, and by exten- 70.3
sion, the average life expectancy 63.5
within a population. In 2001, the aver-
age life expectancy at birth in the
United States was 77 years. Japan had
the world’s highest life expectancy—
81 years. The lowest life expectancy
estimates for the early 2000s were in 22.7
17.8
HIV/AIDS-plagued countries in sub-
Saharan Africa: 34 years for Mozam-
bique and 37 years for Botswana and
Lesotho. 0 (Birth) Age 15 Age 65
Life expectancy is a concept many Source: Japan National Institute of Population and Social Security Research, Latest
people use but few understand. What Demographic Statistics 2003 (2003): table 5-13.
does the U.S. life expectancy of 77
years really mean, and to whom does it
apply? The term life expectancy usually well celebrate her 88th birthday (see
is used as a shorthand way of express- Figure 4). Having survived the major
ing “life expectancy at birth.” Can we causes of death at younger ages, she
conclude that a child born in the has already demonstrated that she is
United States in 2001 can expect to live likely to live longer than the average
to age 77, on average? Not really. As an life expectancy at birth.
infant born that year proceeds through
life, mortality conditions will change.
Individual lives may be cut short by war Life Span
or a devastating plague of some new How high can life expectancy get? The
disease, or may be extended through upper limit is governed by the maxi-
fantastic medical advances. mum life span for the human species.
Life expectancy at birth in 2001 Although the two terms are often con-
applies to no real group, not even to fused, life expectancy reflects the real-
real people born that year. Like the life conditions in a population, while
TFR, life expectancy applies to a hypo- maximum potential life span is a theo-
thetical group of people who pass retical number: the highest age the
through their imaginary lives subject most robust humans could reach.16
to the death rates at each age in 2001. Many individuals outlive the average
Age-specific death rates refer to the life expectancy for their society (12
number of deaths of people within a million Americans were older than 77
specific age group divided by the total in 2001), but no one outlives the maxi-
number of people in that age group. mum human life span.
This can also be expressed as the prob- Experts disagree about the upper
ability of dying at a given age. These limit of the human life span and
probabilities are used to construct a about whether it is possible to push it
life table, or actuarial table, which is to higher levels through medical tech-
used to calculate life expectancy at nology or bioengineering.17 The
birth or at any other age.15 longest anyone is known to have lived
Once she reaches age 65, for is 122 years, five months. This was the
example, a Japanese woman has authenticated age of Frenchwoman
nearly 23 additional years of life Jeanne Calment when she died in
remaining, on average, so she may 1997. There have been reports of
11
 people living much longer but these National mortality levels can
claims are unsubstantiated and are increase when health systems break
highly suspect. The very old often down or when diseases spread to new
exaggerate their age, and the record- populations. Life expectancy in Russia
ing of birth dates and ages is haphaz- declined by more than six years after
ard in many countries. Birth records the breakup of the Soviet Union left
were especially poor when the current public health systems in chaos and
centenarians were born. The number many Russians in poverty. Average life
and percentage of elderly who survive expectancy in Russia recovered after
to extremely old ages are increasing, 1994 but suffered another setback
and eventually someone is likely to toward the end of the decade.21
break Madame Calment’s record. In HIV, the virus that causes AIDS,
October 2003, the reputed oldest liv- is spreading rapidly in many world
ing person was 116 years of age.18 regions. The disease has already
Relatively few humans are favored infected more than 30 million in
HIV/AIDS has with a genetic makeup that will allow sub-Saharan Africa, 6 million in
reduced life them to live past 100. Only two in South Asia, and 2 million in Latin
every 100 Americans born in 2001 can America and the Caribbean. HIV/
expectancy in expect to live past age 100.19 In 2003, AIDS has caused life expectancy at
several African seven countries had an average life birth to fall in several sub-Saharan
expectancy of 80 or 81, and continued African countries, reversing the
countries. mortality declines among the elderly gains in infant and childhood
are likely to push these averages health achieved before the epi-
higher. Many world regions still have demic arose.22
extremely high mortality from easily The HIV/AIDS epidemic is a grim
curable diseases, but in nearly all reminder that the battle against com-
countries people live much longer municable diseases will probably
now than in the past. The average life never be over. Many aspects of mod-
expectancy in the world around 1900 ern life—international air travel,
was less than 30 years of age; in 2003, importation of fruits and vegetables,
it was about 67 years. Thus, since the migration, and even changes in cli-
origin of modern humans some mate—favor the spread of communi-
100,000 years ago, the vast majority of cable diseases.23 Natural disasters and
progress in conquering mortality has widespread violence can also produce
taken place in the minute slice of time a spike in the number of deaths, but
since 1900. Much of the increased life they usually have little long-term
expectancy worldwide reflects the impact on mortality rates at the
accumulation of knowledge about national level. Earthquakes, wars,
how diseases spread as well as fires, terrorism, hurricanes, and other
improvements in personal hygiene disasters claim the most lives in less
and public health practices.20 developed areas, where many people
A large share of the remaining gap live in low-quality housing and where
in mortality between more developed the public health and emergency
and less developed countries can be response systems are limited.
attributed to preventable diseases that
strike children particularly hard,
including diarrhea, respiratory infec- Mortality in the United
tions, measles, and neonatal tetanus. States
Antibiotics, immunization, and clean Life expectancy in the United States
drinking water have drastically —age 77 in 2001—has seen spectacu-
reduced the incidence and severity of lar improvement over an average life
these diseases in the United States expectancy of only age 47 in 1900,
and many other countries. If ade- but it is still less than in Japan, Ice-
quate health services were available land, and a number of other coun-
throughout the less developed world, tries. How can mortality be reduced
mortality could fall quite rapidly. further in the United States? We need
12
first to look at the causes of death. Table 1
Table 1 lists the 15 leading causes of The 15 Major Causes of Death: United States, 2001
death in the United States, which
account for 84 percent of all deaths. Ratio of rates
Heart disease and cancer are the two Deaths per Percent of Male to Black to
Cause of death 100,000 all deaths female white
biggest killers. Indeed, these two dis-
eases are in a league by themselves; 1. Heart disease 245.8 29 1.5 1.3
they are responsible for more than 2. Cancer 194.4 23 1.5 1.3
one-half of all deaths. Heart disease, 3. Stroke 57.4 7 1.0 1.4
cancer, and most of the other major 4. Chronic lower
causes of death strike primarily after respiratory disease
age 50 rather than during childhood. (emphysema, bronchitis) 43.2 5 1.4 0.7
But no one is immortal. All the 5. Accidents
(unintentional injuries) 35.7 4 2.2 1.0
progress in life expectancy has, after
6. Diabetes mellitus 25.1 3 1.2 2.1
all, only postponed death.
7. Pneumonia and
influenza 21.8 3 1.4 1.1
8. Alzheimer's disease 18.9 2 0.8 0.7
Mortality Differentials 9. Kidney disease 13.9 2 1.5 2.4
The Grim Reaper does not bring 10. Septicemia
death to all on an equal basis. Death (blood poisoning) 11.3 1 1.2 2.3
rates vary by common social cate- 11. Suicide 10.8 1 4.6 0.5
gories such as age, sex, socioeco- 12. Chronic liver disease
nomic status, race, ethnicity, and and cirrhosis 9.5 1 2.1 1.0
religion. Cultural, political, and other 13. Homicide 7.1 1 3.3 4.3
social factors help explain the gap in 14. Hypertension 6.8 1 1.0 2.9
life expectancy among different 15. Pneumonitis due to
solids and liquids 6.1 1 1.8 1.1
groups of people.24 Genetic factors
also explain why individuals with simi- Source: E. Arias et al., National Vital Statistics Reports 52, no. 3 (2003): table C.
lar background characteristics die of
very different causes and at different
ages. Individuals can inherit a predis- Once children survive that crucial
position for developing a potentially first year and the next few years of
lethal disease such as breast cancer. childhood, their life chances improve
Demographic factors—especially age, substantially. Young Americans have
sex, and ethnicity—are also closely less than a 1 percent chance of dying
tied to mortality rates. between ages 15 and 24. But that 1
percent attrition means that about
Age 40,000 15-year-olds will never reach
Death in the first year of life (infant their 25th birthdays.
mortality) is an important demo- Most of these deaths are socially
graphic variable and is often used as a preventable. Indeed, the rank order
key measure of a society’s quality of of causes of death for 15-to-24-year-
life. The infant mortality rate (IMR)— olds is very different from that shown
the number of deaths among infants in Table 1 for the entire population.
under age 1 per 1,000 live births— Injuries cause the most deaths in this
declined tremendously in the United age group, led by injuries from motor
States during the 20th century. In vehicle crashes. Accidents (uninten-
1900, about 120 newborns died out of tional injuries), homicide, and suicide
every 1,000 babies born alive. By 2003, are ranked one, two, and three and
the infant mortality rate was 7, low by accounted for 71 percent of all deaths
world standards but still higher than in that age group in 2001.
in many European countries. In coun-
tries where health care systems are Sex
inadequate and infectious diseases are Women have lower death rates than
rampant, the IMR often exceeds 100 men at every age, probably because of
deaths per 1,000 live births. a combination of social, behavioral,
13
 and genetic influences. Even before female life expectancy was nearly five
birth, fewer female than male fetuses years lower than that of white females.
die in the womb. The net result of Similarly, black male life expectancy
this female advantage is that women was six years below that of white
live longer than men, as illustrated males, placing black males at the
for Japanese women in Figure 4 bottom of the mortality totem pole.
(page 11). In the United States, African Americans die at younger
female life expectancy was 80 years in ages than whites because they are
2001, nearly six more years than that more vulnerable to 11 of the 15 lead-
of men. About four-fifths of American ing causes of death shown in Table 1.
centenarians are women. Note especially the ratio of black to
The sex differential in mortality white homicide death rates—the rate
rates is greatest for young adults. The is more than four times higher for
death rate for 15-to-24-year-old males blacks than for whites.
is nearly three times greater than Minorities do not always have
that of their female counterparts. higher mortality. Infant mortality
Notice first that all the leading causes rates for Hispanics and Asian Ameri-
of death listed in Table 1 (page 13) cans are at least as low as the rate for
kill males at a higher rate than non-Hispanic whites.26
females. Which causes have the high-
est male-to-female ratio? They are
accidents, which tend to befall more
young men because they are more Migration
likely to engage in risky behavior; sui- The third component of population
cide, which claims more than four change is migration, the movement
times as many male as female lives; of people into or out of a specific
and homicide, which kills three times geographic area. Migration adds to or
as many men as women. In short, the subtracts from an area’s population
sex differential in mortality is great- depending on whether more people
est between ages 15 and 24 because move in or out. Migration usually has
the major causes of death in those the greatest impact on population
ages are also the ones with the high- change in small geographic areas and
est male-to-female ratio. where there is little or no natural
increase from the excess of births
Socioeconomic Status over deaths. Migration trends can
Higher-status individuals live healthier also shift the population distribution
and longer lives than their lower-status within a country.
counterparts in virtually every society. Migration is the most complex and
The United States is no exception. All volatile demographic variable. It can
the major indexes of social status— occur in great waves in response to
occupation, income, and education— major events—such as the mass exo-
show a negative relationship between dus from East to West Germany after
status and mortality.25 these countries were reunited in
1990—or as a slow trickle, such as the
Race and Ethnicity attrition of young adults from small
Racial and ethnic minorities often suf- towns in the rural Midwest.
fer greater premature mortality than Migration is selective. More edu-
others, usually because they are also cated and more adventuresome peo-
economically disadvantaged. African ple are more likely than other people
Americans have always had higher to move, for example. Migration is
mortality and lower life expectancy closely tied to the life cycle. People
than whites in the United States. The are most likely to move at certain
gap in life expectancy between the stages of their lives, especially when
two races was about 15 years in 1900 they marry, divorce, or retire.
and nearly six years (78 for whites Migration is also more difficult to
versus 72 for blacks) in 2001. Black measure than fertility and mortality.
14
Most countries do not have an easy Table 2
and accurate way to track population U.S. Population in 2000 by
movements. Every year, millions of Residence in 1995
Americans move to a new home, but
not all such residential mobility is Population
classified as migration. Neither are Type of move in millions Percent
temporary moves for work or leisure. Total, ages 5+ 262.4 100
Migration refers only to the move- Nonmovers 142.0 54
ment of people across a territorial Movers 120.3 46
boundary for the purpose of chang- Within same county 65.4 25
ing their place of usual residence. From different county,
International migration involves same state 25.3 10
movement across a national border. From different state 22.1 8
From abroad 7.5 3
The terms immigration and emigra-
tion describe whether people are Source: B. Berkner and C.S. Faber, “Geographical Mobility:
moving into (im-) or out of (e-) a 1995 to 2000,” Census 2000 Brief (2003): table 1. Migration is the
country. Internal migration describes most complex
moves within a country. In the United and 3 percent moved from another
States, people must move across a country (see Table 2). Americans are and volatile
county line to be an official migrant. more mobile than residents of most demographic
Other countries define migration dif- other countries. In Japan, for exam-
ferently—as movement to another ple, only 28 percent of the population variable.
municipality, for example. The terms age 5 or older moved to a new resi-
in-migration and out-migration refer dence between 1995 and 2000.
to movement into or out of a specific Local, or intracounty movers, gen-
county, state, or other political juris- erally are making housing adjust-
diction within a country. ments or responding to life-cycle
Net migration, the difference changes such as leaving the parental
between the number of people mov- home or getting married or divorced.
ing in and the number moving out, Longer distance moves are primarily
may be positive or negative. Between for economic reasons such as seeking
2000 and 2002, Florida had a net a new job or accepting a corporate
gain of 633,000 people through transfer. People also move long dis-
migration from abroad and from tances to attend school, to find a
other states, while New York state more amenable climate, to adopt
suffered a net loss of 43,000 people a new lifestyle, or to live closer to
from migration.27 The United States family members. High levels of resi-
as a whole experienced a net immi- dential mobility can foment social
gration of 3.3 million people from problems, especially if the moves dra-
abroad between 2000 and 2002. matically change the age, racial, eth-
In the less developed world, where nic, or socioeconomic characteristics
internal migration is dominated by of the population in the place of ori-
moves from the countryside to the gin or destination.28
cities, rural areas often experience
high net out-migration while urban
areas undergo high rates of net in- Who Moves Most Often?
migration. In the United States and most other
countries, residential mobility is rela-
tively high for children under age 5;
Types of Moves relatively low during the mid-teens;
Most moves are local, short-distance and extraordinarily high for people
moves. International moves are the in their early 20s. Thereafter mobility
least common. Between 1995 and rates decline with age, rapidly at first,
2000, nearly one-half of Americans and then more gradually until about
moved to another residence, but only age 85, when there is a slight upturn
8 percent moved from another state, (see Figure 5, page 16).
15
Figure 5 Income, Education, and
People Who Moved Last Year, by Age: United States, Ethnicity
2001 Non-Hispanic whites tend to move less
Percent of population who moved within year often than African Americans, Hispan-
35 ics, and other racial groups. Between
1995 and 2000, 43 percent of non-
30 Hispanic whites moved compared with
49 percent of blacks, 54 percent of
25 Asians, and 56 percent of Hispanics.30
One reason blacks and Hispanics
20 move more often than whites is that
they are more likely than whites to
15 rent rather than own their residences,
and renters tend to move more often
10
than homeowners. It is not surprising,
5
then, that blacks and Hispanics are
most likely to move short distances—
0 to another home in the same county.
0-4 15-19 30-34 45-49 60-64 75-79 85+ There is no simple link between
Age residential mobility and income. The
Source: U.S. Census Bureau, “Geographic Mobility: March 2000 to March 2001 Detailed propensity to move depends more on
Tables” (released March 31, 2003; www.census.gov/population/www/socdemo/migrate/
cps2001.html, accessed Oct. 1, 2003): table 1A.
the type of jobs people hold. Doctors,
lawyers, and others who rely on local
bases of operation have low rates of
Young adults are the prime movers mobility, for example, while business
(if not yet shakers) in most societies. executives are highly mobile.
Mobility is highest between the late Educational attainment is also
teens and the early 30s as individuals related to mobility. The most fre-
leave their parents’ homes to attend quent movers are individuals at the
college, find jobs, get married, and educational extremes—the high
build families. The children of these school dropouts and the college edu-
young parents have high mobility as cated. Those in the middle, people
well. As these parents buy homes and who complete high school but do not
settle into neighborhoods and go on to college, have the lowest
careers, their mobility and that of mobility rate. Hispanics have higher
their children (by this time, in their high school dropout rates than other
teens) declines. Most of the elderly major ethnic and racial groups, a fac-
stay put, but a sizable minority trade tor that helps explain their higher
their homes for smaller residences or average mobility rates.
eldercare facilities, or move to far- The distance of moves differs by
away retirement areas.29 education. The best educated make
relatively more long-distance moves;
Men and Women the least educated tend to make
U.S. women are about as likely as U.S. more local moves. This also helps
men to move, but the rapid increase explain why U.S. Hispanics and
in mobility in the young adult years African Americans, who have lower
starts earlier for women than for men average educational attainment than
because women tend to marry at whites, make more short-distance
younger ages than do men. moves than do whites.
In many Latin American countries,
young women are at least as likely as
young men to leave home in search International Migration
of jobs elsewhere. In African coun- In recent decades, international
tries, however, men are more likely to migration streams of one sort or
move to the city to find work, often another have made headlines around
leaving wives and children behind. the world—the dramatic influx of
16
Rwandan refugees into Zaire and Tan-
zania, Haitians sailing to the United
States in flimsy boats, and Bosnians
fleeing to Germany and other parts of
Europe. An estimated 175 million
people lived outside their country of
birth in 2000—about 3 percent of the
world’s population.
These migrations occurred for the Photo removed for copyright reasons.
traditional reasons—the migrants
either wanted to upgrade their lot in
life or escape from harsh, often intol-
erable circumstances. Migration
experts often describe the process as a
push-pull process: Migrants are
“pushed” from their homeland by dif-
ficult conditions and “pulled” to a new
country where conditions appear to
be better. But there are a number of
theories about what forces affect People are most likely to move when they
migration.31 cross major thresholds in their lives, such as
Migrants who leave home to avoid going to college, getting married, or retiring.
persecution because of their political,
religious, or ethnic backgrounds are and Asia. At least 200,000 U.S. resi-
classified as refugees or asylees. These dents emigrated each year in the early
“involuntary” migrants are protected by 2000s. Most are immigrants moving
international law, although they are on to other foreign countries or
not always welcomed by the countries returning to their countries of origin.
in which they seek protection. National Some are U.S. citizens taking jobs
governments must decide who is or is abroad or retirees moving to countries
not a legitimate refugee or asylee, and with lower costs of living.
they sometimes send such foreigners
home. In 2003, there were an esti-
mated 20 million refugees, asylees, or Immigrant Characteristics
displaced people around the world, International migrants differ from the
according to the United Nations High compatriots they leave behind and
Commissioner for Refugees.32 The from the residents of the countries in
United States is traditionally a country which they settle. They differ from
of immigrants, and receives twice as one another depending on why and
many immigrants as all other countries how they arrived in a new homeland.
combined. More than 1 million new-
comers have immigrated to the United Age
States annually over the past few Young adults and their children are
years—the highest level since the mass more likely than older individuals to
immigration of Europeans in the immigrate to a new country. The
decades before and after 1900. immigrant flows to the United States
During the 1990s, about 900,000 traditionally have been dominated by
people a year entered the United young adults. The present U.S. immi-
States as legal immigrants. Another gration policy, with its guiding princi-
350,000 to 500,000 a year were illegal ple of family reunification (giving
immigrants.33 The numbers seeking to preference to relatives of previous
enter the United States are not likely immigrants), has reduced the propor-
to abate in the near future because of tion of young adults among recent
continuing population and economic immigrants. Refugees can be much
pressures in the less developed world, more varied in age—they may include
particularly in Mexico, the Caribbean, more families with small children,
17
 elderly individuals, or young men— percent of the U.S.-born population
depending on the circumstances that age 25 or older. The proportion of the
brought them. foreign-born completing high school
was much greater for immigrants from
Sex Africa (95 percent) and from Asia (84
Males have traditionally outnumbered percent) than it was for immigrants
females among immigrants. An extreme from Latin America (50 percent).
example of this phenomenon was the Legal immigrants tend to have
27-to-1 male-to-female ratio among Chi- higher educational attainment than
nese immigrants to the United States in illegal immigrants; and refugees tend
the early 1900s. Today that ratio is about to have lower average attainment than
1-to-1 for immigrants.34 other legal migrants. More recent
The sex ratio of immigrants varies immigrants are less likely to have a
throughout the world, depending on high school diploma than native-born
the types of jobs available in the coun- Americans, but they are also more
About half of try of destination and the cultural cli- likely to have a college degree.36
U.S. legal mate in the country of origin. Labor Statistics on occupation and income
immigrants to the Middle East are pre- tell a similar story. Among the largest
immigrants dominately men, for example, in part immigrant groups, Asians have a rela-
come from because there are few jobs for women tively high socioeconomic status and
in Islamic Middle Eastern countries. Hispanics a relatively low one. During
Latin America. the 1980s and early 1990s, however, an
Race and Ethnicity influx of less-educated refugees from
The vast majority of immigrants to the Southeast Asia injected more eco-
United States between the early 1800s nomic diversity into the Asian Ameri-
and the mid-1960s were Europeans; can population. While the average
but Europeans accounted for only incomes of Asians remain higher than
about 13 percent of legal immigrants for other groups, growing numbers of
in the 1990s. About 51 percent of legal U.S. Asians are at the bottom of the
immigrants came from Latin America socioeconomic ladder.37
and another 30 percent from Asia.35
Immigration is changing the ethnic
composition of the United States, Aus- The ‘Brain Drain’
tralia, Canada, Germany, and many When educated and highly skilled peo-
other countries. ple emigrate to a new country, their
home country loses. Not only does the
Socioeconomic Status home country lose its investment in
Often the more ambitious and adven- raising and educating those expatri-
turesome people in a poor society are ates, it also loses their potential social
the ones who migrate. Migrants tend and economic contributions.38 This
to be more educated than others in “brain drain” is not just a problem for
their home community, but less edu- less developed countries such as India
cated than the residents of the country and Nigeria. Many scientists, engi-
to which they are moving. Immigration neers, and college professors from
laws can affect the types of people who Great Britain and other more devel-
come in, for example, by restricting oped countries have immigrated to the
visas for unskilled workers, encourag- United States for higher salaries and
ing the entry of highly educated pro- greater professional opportunities.
fessionals, or accepting refugee
families from a specific country.
The educational and socioeconomic Migration and Social
status of immigrants varies greatly Networks
among individuals and groups. In 2000, Individuals usually do not uproot
67 percent of the foreign-born popula- themselves and their families at ran-
tion age 25 or older had at least a high dom to move to another area; nor do
school education, compared with 87 they choose their place of destination
18
by flipping a coin. Migration is a
social process involving networks that
connect the place of origin to the
place of destination. The movement
of individuals takes place through
chain migration, defined as move-
ment in which prospective migrants
learn about job opportunities, trans-
portation, and housing in the place Photo removed for copyright reasons.
they want to move to from relatives or
friends from their home area who
have migrated ahead of them.39
Chain migration operates in both
international and internal migration.
In the former, a few bold immigrants
blaze a trail to a new country, establish
a foothold, and then send for friends
and family to join them. These indi- International migration is at an all-time high. Most immigrants are
viduals form small ethnic communi- prompted by a desire for better economic conditions, but some are refugees
ties, such as the Chinatowns in cities escaping starvation or political persecution.
throughout the world, which act as
magnets (or pull factors) for others in
the place of origin. Most immigration Population Size
to the United States has followed this
pattern. Hispanic and Asian immi- and Growth
grants often join established commu- Whether a population grows or
nities of their compatriots, such as wanes, the changes can be traced to
Little Saigon in Southern California’s the net effects of the three demo-
Orange County. U.S. immigration pol- graphic processes already discussed:
icy strengthens migration networks by fertility, mortality, and migration.
granting entrance visas to close rela- Fertility adds members to the
tives of current U.S. residents. population and mortality removes
Chain migration also plays an them. Thus, the annual number of
important role in rural-to-urban migra- deaths in a population can be sub-
tion. The presence of a network of rel- tracted from the annual number of
atives and friends in a particular city births to find the net number of peo-
attracts rural out-migrants to that city. ple added through natural increase as
These networks help ease the financial summarized by the demographic bal-
and social problems associated with ancing equation (see Box 3, page 20).
relocation. While chain migration is In 2002, there were 1.6 million more
not as important in the United States births than deaths in the United
today as it was in the past, many Amer- States. Worldwide, there were 81
icans cite family-related reasons for million more births than deaths.
moving to a new residence.40 The death rate can be subtracted
When it comes to social networks, from the birth rate to find the rate of
migration is a two-edged sword. natural increase. The estimated crude
While it may provide new opportuni- death rate for the United States in
ties for the migrants, migration often 2003 was 8.5 deaths per 1,000 inhabi-
tears individuals away from a network tants. Subtracting this from the 2003
of relatives and lifelong friends who crude birth rate of 14.1 yields a rate
provided valuable financial, health of natural increase of 5.6 additional
care, and other support.41 It is no people per 1,000 inhabitants, or as it
wonder that migrants seek neighbor- is more commonly expressed, 0.6 per-
hoods in their new countries that cent. The birth rate and the death
bring them back to the embrace of rate for the world were 21.5 and 8.7,
familiar social networks. respectively, which produced a rate of
19
 natural increase of 1.3 percent, more Washington, D.C. Births, deaths, and
than twice the U.S. rate. The rate of in- and out-migrants sometimes cancel
natural increase is added to the rate each other out and produce neither
of net migration to yield the overall growth nor decline.
population growth rate. The rate of growth can be used to
Populations increase through estimate a population’s hypothetical
migration and natural increase in doubling time, which is the number
most places; but populations may also of years until the population will dou-
decline, as they have in Russia and ble if the rate of growth remains con-
stant. Doubling time can be estimated
by dividing the number 70 by the
Box 3 growth rate expressed as a percent-
The Demographic Balancing Equation age. A population growing at 2 per-
Populations grow or decline as the result of three processes: cent annually, for example, would
birth, death, and migration. These three variables are the double in 35 years; one growing at 1
components of population change and often are depicted percent would double in 70 years.
in the population balancing equation. To show population When the rate of population growth
change between 2001 and 2003, the equation would look is negative or zero, of course, the
like this: population will never double.
Population in 2001
+ Births
– Deaths
World and National
+ Immigrants Populations
– Emigrants World population in 2003 was 6.3 bil-
= Population in 2002 lion and was growing at a rate of about
1.3 percent annually. World population
Births minus deaths constitute natural increase. When deaths is growing today because births exceed
exceed births, as they do in Germany, the result is natural deaths by a wide margin—by 81 million
decrease. Subtracting emigrants from immigrants yields net in 2003. Net migration, of course, is
migration, which also can be either positive or negative. not a factor in world population
growth, and it never will be unless colo-
Births Immigrants
– Deaths – Emigrants
nizing other planets becomes a reality.
= Natural increase = Net migration The actual world population in 2050
or thereafter is unknown. But demogra-
The balancing equation for the United States is shown below: phers can project the future population
of the world or a country. Beginning
Starting Population with current estimates of population
July 1, 2001 285,317,559 size and growth rates (see Box 4), they
make assumptions—really educated
+ Births + 4,047,642 guesses—about how much fertility,
– Deaths – 2,445,837 mortality, and migration rates will
= Natural Increase + 1,601,805 change. A country’s projected popula-
tion in 2050, for example, equals its
+ Immigrants + 1,664,334
current size plus the total births and
– Emigrants – 215,000
= Net Migration + 1,449,334
immigrants expected from now until
2050 (under the assumed rates), minus
Ending Population the expected deaths and emigrants.
July 1, 2002 = 288,368,698 Using these basic principles, the
United Nations recently projected that
Note: The immigration and emigration figures are PRB estimates. The actual numbers of world population will be about 8.9 bil-
people leaving and entering the country each year are not known. lion by 2050, assuming continued
Source: U.S. Census Bureau, “Births, Deaths, and Migration for 2002 declines in fertility and mortality rates.42
by State” and “Annual Population Change: 2000-2002” (released China is the world’s most populous
Dec. 27, 2002; http://eire.census.gov/popest/data/states/tables/
ST-EST2002-04.php and http://eire.census.gov/popest/data/national/
nation, with a 2003 population of 1.3
tables/NA-EST2002-03.php, accessed Oct. 1, 2003). billion. Its population is increasing by
0.6 percent each year assuming mini-
20
mal net migration. India has fewer fertility or increase in emigration. The
inhabitants (1.1 billion) but a higher population of the African continent is
annual growth rate (about 1.7 per- growing at 2.5 percent, yielding a dou-
cent). India is likely to surpass China bling time of only 28 years.
as the world’s most populous country In contrast, many countries are
before the middle of the 21st century. experiencing extremely slow growth
Most of the world’s fastest-growing and even natural decrease because
countries are in the Middle East and death rates have risen above birth
Africa. Yemen’s 2003 population of rates. Deaths exceeded births in 17
19.4 million is growing by about 3.3 European countries (including Ger-
percent per year. At that rate, the many, Italy, and Russia) in 2003. In
population will double in 21 years some countries, net immigration pro-
unless there is a significant decline in vides the only population growth.

Box 4
Where Do Demographic Data Come From?
Demographers use a variety of rates, ratios, and A few countries (Sweden, for example) have com-
other measures to study population.1 But these mea- prehensive registration systems, or national popula-
sures are only as accurate as the data from which tion registries, that track individuals from birth to
they are calculated. Where do these demographic death and record changes in their residence or mari-
data come from? How accurate are they? tal status.
Most demographic measures are based on counts Surveys often provide estimates of demographic
of people or demographic events (for example, events where registration systems are inadequate.
births) in a specific area during a specific time period. They also aid in developing estimates of population
There were 281,422,509 residents in the United States size during the long interval between censuses. Sur-
in April 2000, for example, and 1,730,000 births in veys usually collect data for a sample group within a
Iran during 1990. Counts come from population cen- specific geographic area. In the United States, a
suses, vital registration systems, national registers, and monthly national survey is used to track the unem-
surveys. Their accuracy varies greatly by country and ployment rate as well as many demographic indica-
even by regions within countries. tors. But surveys suffer from many of the same
The population census—an enumeration of all accuracy problems as censuses and registration sys-
households—forms the cornerstone of demographic tems, and their data are subject to varying degrees
analysis. More than 90 percent of the world’s popula- of error.
tion was covered in national censuses in the last Demographers have developed statistical tech-
decade. Census counts are less accurate and com- niques to overcome some of the shortcomings of
plete in populations with low literacy and poor trans- the basic data with which they work. They apply
portation networks. these techniques to the best data available to com-
The population characteristics that censuses pute estimates of the actual population counts and
record also are subject to error. Residents may lie measures. Although estimates based on good data
about their income or forget the exact ages of some can be quite accurate, users of these estimates
household members. Sometimes census results are should not forget that estimates are only approxi-
manipulated to bolster the numbers in a specific eth- mations of the true number.
nic group or geographic region to favor the ruling Likewise, users of demographic data always should
political party. question the source and quality of the data that
Vital events—births, deaths, marriages, and underlie the rates, ratios, and proportions they cite.
divorces—are usually recorded in national vital reg- Judging the quality of data is one of the most impor-
istration systems. These are the source of the counts tant skills demographers must learn. Indeed, every-
used to calculate fertility, mortality, marriage, and one would benefit from taking a hard look at the
divorce rates. But in countries in which mothers myriad of statistics we encounter daily.
give birth at home or where many residents are illit-
erate, a large proportion of vital events are never References
recorded. Less than half of the world’s population 1. Arthur Haupt and Thomas T. Kane, Population Handbook,
lives in countries that have “complete” vital registra- International Edition, 4th ed. (Washington, DC: Popula-
tion systems. Even “complete” systems may miss up tion Reference Bureau, 1998); and John R. Weeks, Popu-
to 10 percent of a country’s vital events. lation: An Introduction to Concepts and Issues, 8th ed.
(Belmont, CA: Wadsworth/Thompson Learning, 2002).

21
 U.S. Population accounted for as much as one-half of
The United States is the third most population growth during the 1990s.
populous nation in the world, trailing Because fertility and mortality are
only China and India. The U.S. Census expected to remain at relatively low lev-
Bureau estimated that the U.S. popula- els in the United States, the most
tion increased by 3.1 million between volatile demographic variable driving
2001 and 2002 because the number of future growth is immigration.
births and immigrants exceeded the U.S. population has been projected
number of deaths and emigrants. Note to reach 420 million by 2050.43 But we
the relative contribution made to should remember that these projec-
growth by natural increase and net tions are based on educated guesses
migration in Box 3 (page 20). Net about future trends in fertility, mortal-
migration of legal and illegal migrants ity, and migration.

Individuals Box 5
Households and Families
relate to
Individuals relate to society through describe and measure Americans’ living
societies their families and households. When arrangements beyond the family/non-
through their these units add or lose members—or family dichotomy, with terms such as
when the household members grow cohabiting or unmarried couples and
families and older, divorce, or marry—there can be POSSLQs (Persons of the Opposite Sex
households. profound social and economic conse- Sharing Living Quarters).2
quences. Divorce can bring financial An individual’s living arrangements
hardship. Marriage can add additional usually change at different stages of life.
income, as well as stepchildren or In the traditional scenario, a person
mothers-in-law. The birth of a child can starts out in a family household, leaves
bring new financial expenses, but it to create a new household alone or with
also can encourage stability. friends, then forms a family household
Households and families are basic with a spouse and eventually children.
units of analysis in demography. They In old age, an individual may live in a
are not the same thing. A household is single-person household again because
composed of one or more people who of divorce or death of the spouse. Of
occupy a housing unit.1 Not all house- course, not everyone follows this pat-
holds contain families. Under the U.S. tern; many people skip or repeat stages.
Census Bureau definition, family The average size and composition of
households consist of two or more indi- households are highly sensitive to the
viduals who are related by birth, mar- age structure of the population. But
riage, or adoption, although they also they also reflect social and economic
may include other unrelated people. changes. An economic squeeze may
Nonfamily households consist of peo- prolong the time adult children live at
ple who live alone or who share their home; a rise in the divorce rate may
residence with unrelated individuals. increase the number of single-person
These official definitions do not nec- households. Relaxed social rules about
essarily reflect changing attitudes about marriage may boost the number of
marriage, childbearing, and the roles unmarried couples setting up house.
of men and women. Households that In the United States, the mix of
consist of unmarried couples living household types has changed enor-
together and gay and lesbian couples, mously over the last three decades.
for example, would be counted as non- One of the most notable changes is the
family households even though they proportion of family households and
might share many characteristics of a the rise in single-person households. In
family. If these couples live with chil- 1970, 81 percent of all households
dren from their current or a previous were family households, but this was
relationship, the household moves into down to 68 percent by 2003.
the family category. The Census Bureau The retreat from marriage and the
has been exploring new ways to general aging of the population are

22
Population ages of all its members. This Population
Bulletin focuses on age, sex, race, and
Composition ethnicity because these characteristics
People have many characteristics with are fashioned solely by the prime
demographic dimensions—including demographic forces of fertility, mortal-
their sex, age, race, ethnicity, occupa- ity, and migration.
tion, education, religion, marital status,
and living arrangements (see Box 5). A
population has corresponding charac- Age and Shape of
teristics constructed from personal Societies
traits of individual members. The age The age composition of a society can
composition of a population, for exam- be depicted by a population pyramid,
ple, is determined from the collective a figure that shows the proportion of

increasing the number of single-person 2. Suzanne M. Bianchi and Lynne M.

households. Americans are waiting Casper, “American Families,” Population
longer to get married, if they choose to Bulletin 55, no. 4 (2000): 3-6, and 14; and
marry at all. Married couples are more Jason Fields, “Children’s Living Arrange-
likely to get divorced than they were in ments and Characteristics: March 2002,”
the 1970s. More of America’s elderly Current Population Reports P50-547 (2003).
live alone after the death of a spouse.
In 2003, 26 percent of all U.S. house- U.S. Households
holds consisted of just one person, Percent of households
compared with 17 percent in 1970 (see
figure). Many European countries have 1970 2003
seen a similar rise in single-person Single
households for similar reasons. person Nonfamily Single
The U.S. baby-boom generation has- 17% households person
tened many of the changes in the 26%
Other nonfamily
makeup of U.S. households. When the 2%
first of the baby-boom generation
entered their late teens and early 20s Other nonfamily
6%
in the 1960s, they moved out of their
parents’ homes and set up their own
households, often alone or with house-
mates. They waited longer to marry
than the previous generation, and they Married-
couple Married-
were more likely to divorce. family Family couple
Americans born after the baby boom 70% households family
are delaying marriage even longer. In 52%
1970, 89 percent of women ages 25 to
29 had been married at least once. In
2002, only 60 percent of women ages 25
to 29 had been married. The choices
these women make about marriage and
childbearing help determine the pre- Other
Other family
sent and future makeup of U.S. families family 16%
and households. 11%
Sources: U.S. Census Bureau, “Households by Size:
References 1960 to Present” and “Households by Type: 1940 to
1. Jason Fields and Lynne M. Casper, Present” (released June 12, 2003; www.census.gov/
population/socdemo/hh-fam/tabHH-4.xls and
“America’s Families and Living Arrange- www.census.gov/population/socdemo/hh-fam/
ments,” Current Population Reports P50-537 tabHH-1.xls, accessed Sept. 30, 2003); and PRB
(2001): 1. analysis of data from the 2003 Current Population
Survey (March Supplement).
23
 Figure 6
Population Pyramids: Mali, United States, and Italy, 2000
Rapid Growth Slow Growth Decrease
Mali Age United States Year of birth Italy
80+ Before 1919
75-79 1920-1924
70-74 1925-1929
65-69 1930-1934
60-64 1935-1939
Male Female 55-59 Male Female 1940-1944 Male Female
50-54 1945-1949
45-49 1950-1954
40-44 1955-1959
35-39 1960-1964
30-34 1965-1969
25-29 1970-1974
20-24 1975-1979
15-19 1980-1984
10-14 1985-1989
5-9 1990-1994
0-4 1995-1999
10 8 6 4 2 0 2 4 6 8 10 10 8 6 4 2 0 2 4 6 8 10 10 8 6 4 2 0 2 4 6 8 10
Percent of population Percent of population Percent of population
Source: U.S. Census Bureau, International Data Base (updated July 17, 2003; www.census.gov/ipc/www/idbpyr.html, accessed Sept. 30, 2003).

the population in each age group cohort that will survive to enter the
(see Figure 6). In 2000, about 19 per- next age group.
cent of the population of Mali was The majority of people in rapid-
under age 5, while only about 3 per- growth societies are young. This cre-
cent was age 65 or older. The sum of ates tremendous momentum for
the proportions in all age groups future growth because that large pool
equals 100 percent of the population. of young people makes up the parents
There are three general types of of the future. Even if they have only
population pyramids: those depicting four children apiece (the average for
rapid growth, slow growth, and popu- some less developed countries), their
lation decline. A rapid-growth popula- children’s generation would be twice
tion is the only one that really looks the size of their own. Mali’s popula-
like a pyramid because each age tion age structure is typical of a young,
cohort is larger than the one born rapid-growth society.
before it. This pyramid shape results A population that is not growing,
primarily from sustained high fertility. or is decreasing, produces a very dif-
If couples in one generation average ferent shape. The base of Italy’s popu-
eight children, for example, their lation “pyramid” is narrowing because
children’s generation will be about its birth rate has been falling. The
four times larger than their own. The 1995-1999 birth cohort was barely
pyramid’s base would be about four one-half the size of the 1965-1969
times as wide as its middle. cohort. If fertility remains below
The distinctive pyramid shape also replacement, the pyramid’s base will
results from declines in mortality. continue to constrict, and Italy will
Because of high mortality in the past, undergo natural decrease. If Italy’s
older age groups have relatively few TFR rises to the replacement level of
surviving members and occupy a 2.1, its age and sex structure would
small section of the pyramid. The eventually assume a rectangular shape
base is broadened by the fact that because similar numbers of births
mortality, particularly infant mortal- would occur each year. Because mor-
ity, is declining. This increases the tality is low, this shape would be main-
proportion of the younger birth tained until the older ages, when
24
mortality would eat away at the top More than four-fifths of the world’s
bars. At the very top, the female bar is population lives in less developed
almost always longer because women countries, and the world’s overall
live longer than men. median age is young—about 26 years.
A slow-growth population is gener-
ally in the process of changing from a
rapid-growth to a near-zero growth U.S. Age Structure
shape in response to changes in fertil- The age structure of the United States
ity and mortality. The United States is looks more like a bowling pin than a
typical of these “middle-age,” slow- pyramid (see Figure 6). This shape was
growth societies. created by drastic swings in the num-
Population pyramids also can be ber of births—from the historic low of
shaped by migration. Because migra- the 1930s, to the baby-boom peak of
tion is age selective, it alters the shape 1957, down to the baby-bust low of the
of age-sex pyramids in both the place mid-1970s, and back to the baby
of origin and destination. Migrants boomlet of the 1980s and early 1990s.
tend to be young adults; a steady The pyramid’s middle-age bulge is
migration stream is likely to make the composed of the baby-boom cohort,
place-of-origin population older, and which has been likened to a swallowed
the place-of-destination population pig moving through a python.45 The
younger. There are plenty of excep- narrower base is made up of the baby-
tions to this pattern. Migration streams bust cohorts born since the late 1960s.
that are predominately male—as is Each year the U.S. population gets
labor migration to Middle Eastern older, primarily because of the aging
countries—create an unbalanced pyra- of the baby boomers and low fertility.
mid, illustrated by Figure 8 (page 28). Increases in average life expectancy
Pyramids also reflect historical also have contributed to the aging of
events—wars, famines, baby booms or the population. The U.S. median age
busts, and changes in immigration was 35.7 in 2002, up from 27.9 in 1970.
policies—that have affected one of the The U.S. median age could reach 39
three demographic variables. Con- years by 2050.46
sider the tumultuous events portrayed
in the pyramid for Germany in Figure
7 (page 27). Births plummeted during Effects of Age Composition
the two world wars and a severe eco- The age structure of a society has a
nomic crisis, for example. profound impact on its demographic
and social character. Some of these
Median Age impacts have been noted already—for
Population pyramids depict the gen- example, the effect of age structure
eral shape of a population’s age struc- on population growth and on the
ture, but they do not provide rates or average age of a society. But age struc-
measures that can be compared over ture is relevant to many seemingly
time or with other populations. One unrelated social problems.47
such measure of age composition is The U.S. baby-boom generation
the median age—the age at which provides a vivid example of the var-
exactly half the population is younger ied effects of changing age structure
and half is older. In general, less on society. The baby boomers, born
developed countries have rapidly between 1946 and 1964, are 77 mil-
growing populations with low median lion strong—much larger than the
ages, while more developed countries cohort that preceded them, and
have slow-growing or declining popu- larger than the cohort that followed.
lations with higher median ages. Niger They produced the bulge in the age
and Uganda had a median age of 15 pyramid for the United States seen
in 2000, compared with 40 for Ger- in Figure 6.
many, Italy, and Switzerland and 41 As they passed through each stage of
for Japan.44 the life cycle, the baby boomers faced
25
 Similarly, population aging eventu-
ally increases the proportion of the
population that is disabled or chroni-
cally ill. The aging of the large baby-
boom population, along with
improvements in longevity, are
expected to put increasing strains
on the nation’s health and pension
Photo removed for copyright reasons. systems over the next half century.
Although the number of children
is about the same in the early 2000s as
it was during the baby boom, children
now make up a smaller percentage of
the population. The population under
age 18 was about 25 percent of the
2002 U.S. population, compared with
36 percent of the 1960 population.
As fertility rates continue to fall, world population is growing older, creat-
ing new challenges for societies and governments.
Sex Composition
Population pyramids also show the rel-
shortages—in elementary schools, col- ative proportion of men and women in
leges, housing, and employment. The each age group. Small differences are
baby-boom generation often left excess difficult to discern, but some are obvi-
supply in its wake because, by the time ous. Consider the bite out of the male
enough schools or houses were built, side of Germany’s pyramid for people
teachers were trained, and colleges ages 65 to 94 (Figure 7). This indenta-
were expanded, the baby boomers no tion reflects the military casualties of
longer needed them. The 1980s found World War I and World War II and the
colleges scrambling to find students to longer life expectancy for women than
fill slots created for this large cohort. for men at advanced ages.
Real estate prices soared when baby The sex composition of a popula-
boomers began to buy homes, then tion can be summarized by the sex
dropped as they settled down to raise ratio—the ratio of males to females.
families. As baby boomers begin to This ratio is usually expressed as the
retire in coming decades, more social number of males for every 100 females.
and economic stress is expected.48 The sex ratio at birth is about 105
Some analysts see the dramatic change because 105 boy babies are born for
in the age structure as responsible for every 100 girl babies. The world’s sex
many social changes that accelerated ratio in the 1990s was 102. The ratio
during the 1960s and 1970s when the for more developed countries was 95;
baby boomers reached adulthood. for less developed countries, 104.
Crime is also affected by age struc- Sex ratios are determined by the
ture because young adults—ages 18 to now familiar forces—fertility, mortal-
24—are most likely to be involved in ity, and migration. The influence of
crime. The aging of the U.S. popula- migration on the sex ratio is easy to
tion is one reason cited for a welcome assess. The unbalanced sex ratio of
decline in violent crime rates in the late the United Arab Emirates (UAE)
1990s. Young adults may be just as likely came about because the UAE brought
as ever to engage in crime, but crime in thousands of foreigners from Asia
rates have fallen because these youths and other parts of the Middle East to
make up a smaller share of the popula- work in the country’s oil fields and
tion. This illustrates how changes in age construction sites. The majority of
composition can alter the severity of a these labor migrants were men unac-
social problem even if there is no companied by their families. Women
change in the underlying conditions. in the UAE and many other Muslim
26
countries are less likely to work out- Figure 7
side the home than women in Germany’s Population by Age and Sex, 1996
Europe, for example. There were
Age Male Female Year
fewer jobs for women, and relatively
95+ Deficit of men, 1901
few women were recruited from 90 1906
war casualties
abroad. The host governments did 85 from World War I 1911
not want the immigrants to settle per- 80 Decline in 1916
births,
manently and reasoned that the for- 75 Deficit of men, World War I
1921
eigners were less likely to stay if they 70 war casualties 1926
65 from World War II Decline in births, 1931
had families waiting for them back economic crisis 1936
60
home. The effects of this extremely 55 1941
unbalanced immigration pattern are 50 Decline in 1946
evident in the population pyramid for births,
45 1951
World War II
the UAE shown in Figure 8 (page 28). 40 1956
35 Post-World 1961
The sex ratio for the UAE was esti- War II
30 1966
mated at 151 in 2000. 25
baby boom
1971
Mortality influences the sex ratio 20 1976
because males have higher death rates 15
Long-term
1981
than females at nearly every age, 10 fertility decline 1986
beginning with conception. It is possi- 5 1991
0 1996
ble that as many as 150 male fetuses 800 600 400 200 0 200 400 600 800
are conceived for every 100 female
Population in thousands
fetuses. But a large percentage of preg-
nancies spontaneously abort within the Source: Germany, Federal Statistical Office, unpublished tables.
first few weeks, and a woman is more
likely to miscarry a male fetus than a
female fetus, which produces the usual In some nations cultural factors
sex ratio at birth of 105. override the biological advantage that
In the United States, the ratio of women usually have. In Indian soci-
men to women is about equal (a sex ety, for example, women are accorded
ratio of 100) between ages 35 and 39. low status. Girls receive less food,
The ratio declines to below 96 by ages medical care, and familial attention
50 to 54, and keeps falling. For the 85- than boys.49
and-older group, there are about 40 This discrimination is reflected in
men for every 100 women. This pre- the sex ratio of India—estimated at
ponderance of women at the older 107 in 2000. Sons are highly valued in
ages can be seen in the pyramids for many other Asian countries as well,
Italy and the United States on page 24. often to the detriment of daughters.
Fertility affects the sex ratio by The sex ratio for all of Asia was 104 in
influencing the proportion of young 2000, compared with 98 in Latin
people in a population. Any force America and the Caribbean.
that increases the relative proportion
of young people in a society—as does
a high fertility rate—raises the overall Effects of Sex Composition
sex ratio of the society because the Why does the sex ratio matter? It
sex ratio is higher in the younger affects the availability of marriage
ages. A rapid drop in infant and child partners, for one thing. An unbal-
mortality, for example, in response to anced sex ratio in the young adult
large-scale inoculation campaigns or years—because of migration, fertility
the importation of modern medical swings, or war casualties, for exam-
technology, also contributes to the ple—means that there may not be
“younging” of a population. Con- enough men or women for everyone
versely, any force that decreases the to find a spouse. The scarcity of
relative proportion of young people— potential marriage partners is not
such as high mortality or low fertil- merely a personal disappointment for
ity—lowers the overall sex ratio. individuals who really want to get
27
Figure 8 family has been depleted by higher
Population of the United Arab Emirates, by Age and than average rates of unemployment,
Sex, 2000 incarceration, and even death.
Similarly, the sex composition of
80+
75-79
immigrant groups has a bearing on
Males Females the speed and ease with which they
70-74
65-69 adjust to their new society. An immi-
60-64 grant group that contains more men
55-59 than women, for instance, may com-
50-54 pete with native men for marriage
45-49 partners. This possibility, even if it
40-44 does not happen, invites resentment
35-39 against immigrants and even social
30-34 disorganization. Also, men are far
25-29 more likely than women to engage in
20-24 crime, especially men in the young
15-19 adult ages when most people migrate.
10-14 Higher crime rates can create negative
5-9 stereotypes that impair immigrants’
0-4
relations with other Americans.53
10 8 6 4 2 0 2 4 6 8 10
Percent of population
Source: U.S. Census Bureau, International Data Base (updated July 17, 2003; Race and Ethnicity
www.census.gov/ipc/www/idbpyr.html, accessed Sept. 30, 2003). Many population characteristics are
fluid. A person’s age increases con-
stantly, and educational attainment
married; it also affects the social and and marital status can change over
economic structure of a society.50 time. Other characteristics are fixed
Marriage rates, childbearing prac- at birth, like sex. Race and ethnicity
tices, family stability, crime rates, and appear to fall into the second cate-
even the comparative status and gory. An individual cannot change his
power of women and men can be or her ancestors; they are accidents of
influenced by the sex ratio. birth. But how societies evaluate and
In the United States, for example, classify them is highly variable. Race
the annual increases in the number of and ethnicity are defined differently
births during the baby boom created a by different societies. These defini-
“marriage squeeze” in the 1970s and tions, as well as their political and
1980s by producing more women than social significance, change over time.
men in the prime marrying ages. This What are race and ethnicity? They
phenomenon, along with the contin- are not scientific terms. There is no
ued mortality gap between the sexes, consensus about how many races there
has been linked to many of social and are or about exactly what distinguishes
economic changes since the 1960s— a race from an ethnic group. Many
greater percentages of women remain social scientists agree that, while race
single or delay marriage, bear a child may have a biological or genetic com-
out of wedlock, or work outside the ponent, it is defined primarily by soci-
home.51 William Julius Wilson and ety, not by genetics. There are no
other sociologists have speculated that a universally accepted categories. Physi-
shortage of marriageable black males in cal characteristics, such as facial fea-
ghetto areas may have fostered the dra- tures, hair texture, and skin color, are
matic increase in the proportion of often used to identify racial groups, but
births to unmarried women and in fam- these are highly subjective identifiers.54
ilies headed by single women among Ethnicity is usually defined by cul-
African Americans in recent decades.52 tural practices, language, cuisine, and
In poor neighborhoods, the pool traditions rather than biological or
of black men who could support a physical differences. In the United
28
States, ethnicity often refers to the ancestry, for example, and might
national origin of immigrant groups. choose black and Hispanic. Some
The United Nations (UN) pub- Filipino Americans with Spanish sur-
lishes data on ethnic composition names identify themselves as Hispanic
reported by individual countries, but but also as Asian.
the UN warns that the categories are Many Americans have parents from
“not uniform in concept or terminol- different racial backgrounds—a white
ogy. They represent a variety of char- mother and a black father, for exam-
acteristics or attributes, variously ple, or an Asian mother and a white
designated by countries or areas as father. Previously, mixed-race Ameri-
race, color, tribe, ethnic origin, ethnic cans were asked to indicate the race
group, ethnic nationality, and so they most closely identified with, thus
forth … By the nature of the subject, rejecting the ancestry of one of their
these groups vary from country to parents. People with one Hispanic
country—no internationally relevant parent faced the same dilemma.
criteria can be recommended.”55 In accordance with a 1997 OMB Race is defined
decision, the 2000 Census form primarily by
allowed Americans to check more
U.S. Race and Ethnic than one race, but they still must society, not by
Categories choose one ethnic group. About 2.4 genetics.
The U.S. Census Bureau collects and percent of the U.S. population—6.8
publishes information by race and eth- million Americans—were identified
nicity in accordance with federal guide- as multiracial.
lines from the Office of Management Although exact definitions are elu-
and Budget (OMB). In 1997, OMB rec- sive, race and ethnicity are important
ommended that data be presented for variables in the United States and most
five racial groups and two ethnic other countries. The relative size of
groups. The race groups are: (1) white, individual groups sometimes deter-
(2) black or African American, (3) mines their political power and socio-
Asian, (4) American Indian and Alaska economic status. Shifts in racial and
Native, and (5) Native Hawaiian and ethnic composition can alter the social
Other Pacific Islander. The U.S. Census structure and foment prejudice and
Bureau also includes an “other race” social unrest. Such problems often
option for people who do not identify arise from a basic concern that some
with the OMB categories. other group will grow faster than one’s
The two ethnic groups are Hispan- own and, consequently, increase its
ics (or Latinos) and non-Hispanics. importance within the society.
Hispanics are considered an ethnic Changes in racial and ethnic com-
group, not a race, but this distinction position come about through differ-
confuses many Americans. The Cen- ences in the fertility, mortality, and
sus Bureau classifies as Hispanic any- migration of racial and ethnic groups.
one who traces his or her ancestry to Major shifts in racial and ethnic com-
Spain, the Spanish-speaking countries position are occurring in countries
of Latin America and the Caribbean, throughout the world. In South
or any other Spanish culture. Africa, whites are becoming an ever-
Hispanics may be of any race. Most smaller minority, owing to a lower
report themselves as white, but a large birth rate and a higher emigration
number report their race as “other,” rate than those for black or colored
which underscores the confusion South Africans. And in many Euro-
about race and ethnic definitions. In pean countries, immigrant groups
the 2000 Census, 42 percent of His- from less developed countries are
panics checked the “other” race box. growing faster than their hosts, lead-
A small number of Hispanics report ing to anti-immigrant backlashes.56
themselves as black, Asian, or Ameri- Racial and ethnic diversity has
can Indian. Many Dominican Ameri- been a hallmark of the United States
cans and Puerto Ricans have African since colonial times. Waves of immi-
29
 grants from different parts of the World Population
globe, and different fertility and mor- Population is unevenly distributed
tality rates among those groups than among the world’s regions and,
among native-born Americans, have because some regions are growing
kept the racial and ethnic composi- much faster than others, the geo-
tion in flux. This uneven growth con- graphic distribution of population is
tinues, driven by the differences in becoming more unbalanced. The less
fertility, mortality, and migration dis- developed regions encompassed 68
cussed earlier. In 2000, three of every percent of the world population in
four U.S. residents traced their ances- 1950 and 81 percent in 2003 (see Fig-
try to Europe. Hispanics and African ure 9). These regions are projected
Americans are the nation’s largest to contain 86 percent of world popu-
minority groups, but Hispanics are lation by 2050.
growing much faster because of immi- Fertility is the primary cause of the
gration and higher fertility rates. uneven population growth rates
Asians are growing from a trace ele- among world regions, but migration
ment to a sizable minority. Just after also plays a role. Indeed, interna-
2050, the U.S. population is likely to tional migration is at an all-time high.
consist of several large racial and eth- Migrants move from the less-affluent
nic minority groups—with non-His- more developed nations to the more-
panic whites just holding onto the affluent ones (for example, from Por-
lead. But the racial and ethnic cate- tugal to France) and from the poorer
gories in common parlance are less developed nations to relatively
almost certain to be different by then. prosperous ones (from Colombia to
The evolving ethnic composition Venezuela), as well as from less devel-
has a profound impact on almost oped countries to more developed
every aspect of American society, countries (from Mexico to the United
from social values and culture to edu- States, for example).
cation, politics, and industry. More A major feature of population
public schools than before teach non- redistribution within less developed
English-speaking students from a countries is urban growth. The urban
wide variety of cultural backgrounds. population of these nations rose from
In most big-city school districts, white 304 million to 2.0 billion between
non-Hispanics are already a racial 1950 and 2000.57 In many cities, rapid
minority. Because minorities have a population growth quickly over-
younger age structure and higher fer- whelms the public services and hous-
tility than non-Hispanic whites, ing supply, not to mention the supply
minorities will make up an increasing of jobs. Millions of residents cope by
share of the new job entrants in the building makeshift shelters on open
U.S. labor force. land and by trying to make a living on
the streets, often creating their own
informal economic and social systems.
Gigantic shanty towns have sprung up
Population around major cities throughout the
less developed world, a testament to
Distribution the explosive growth in these cities.
Where do the world’s 6 billion-plus
inhabitants live? Demographers
answer the question by keeping tabs U.S. Population
on the distribution of population by Distribution
world region, by country, by province Like world population, the U.S. popu-
or state within countries, by urban lation is unevenly distributed. More
and rural area, and by neighborhood than half the U.S. population lives
within cities. The geographic distribu- within 50 miles of a coastal shoreline.
tion of population is determined by Mountains, deserts, and long dis-
fertility, mortality, and migration. tances, in conjunction with unrelated
30
economic factors, have limited popu- Figure 9
lation growth in many other parts of Changing Distribution of World Population, 1950,
America. 2003, and 2050
Population density, the number of
inhabitants per square mile, ranges 1950 2003 2050
from 1,134 in highly urban New Jersey 9%
9%
to one in Alaska. Many sections of 25% 14% 14%
5%
America’s heartland are sparsely popu- 5%
8% 20%
lated. In 2002, Wyoming had only
52% 7%
499,000 inhabitants—about five peo-
ple per square mile.58 Yet the Midwest- 7% 59% 57%
ern states of Illinois, Ohio, and 9%
Michigan rank fifth, seventh, and
eighth, respectively, in population size.
The distribution of the U.S. popu- More developed regions Less developed regions
lation is always changing because of North America Africa

geographic differences in natural Europe/othera Asia less Japanb

Latin America
increase and net migration. The
Western and Southern states have a Includes Australia, Japan, and New Zealand.
b Includes Oceania except for Australia and New Zealand.
increased the fastest in recent
decades, while the Northeastern Sources: United Nations, World Population Prospects: The 2002 Revision (2003): table A.4;
and C. Haub, 2003 World Population Data Sheet.
states stagnated or declined. The
South is the most populous region of
the country, with 36 percent of the the U.S. population lived in metropol-
population, followed by the Midwest itan areas. In 2000, about 80 percent
(23 percent), the West (22 percent), of the U.S. population lived in metro-
and the Northeast (19 percent). The politan areas.
West is expected to overtake the Mid- A third major migration stream,
west in the next decade.59 which accelerated during the Great
International and internal migra- Depression of the 1930s, led from
tion are the main determinants of economically depressed areas in the
population redistribution in the South to the cities of the Northeast
United States, but natural increase and North Central states. This South-
also plays a role. West Virginia had ern exodus brought millions of
net out-migration during the 1990s— African Americans to Chicago,
more people moved out of the state Detroit, New York, Philadelphia,
than moved in. Yet West Virginia had Washington, D.C., and other cities
more births than deaths, which made that have large African American
up for the exodus. International populations today. Since the 1970s,
migrants settle disproportionately in however, there has been return
certain states and communities, often migration to the South. There is net
close to their ports of entry into the in-migration of blacks and an even
United States. Two-thirds of the U.S. greater influx of other Americans.
foreign-born population lives in just This phenomenon is part of a fourth
six states: California, New York, Texas, and now major stream: the move-
Florida, Illinois, and New Jersey. ment from the Snowbelt states to the
Within the United States, migrants Sun Belt states.
tend to follow several long-established More dramatic and more rapid
migration streams. The first stream than regional shifts in population is
flows from the Eastern Seaboard states the redistribution of population within
westward, a demographic process that and around metropolitan areas.
has occurred since colonial times and Within a decade, city neighborhoods
that ultimately pushed the American can change from middle-class family
frontier out to the Pacific Coast. The homes to densely populated ghettos of
second stream runs from rural to non-English-speaking immigrants.
urban areas. In 1910, 38 percent of Rolling farmland 30 miles from down-
31
 town can quickly sprout dense town- areas, middle- and upper-income
house developments. Because these Americans are leaving central cities
changes affect a community’s tax base, and low-income suburbs for wealthier
public school enrollment, student- suburbs or neighboring rural coun-
body composition, traffic congestion, ties. They leave behind groups that
and public services, they often spark are disproportionately poor. This
contentious political battles. concentrates the negative social and
Metropolitan areas consist of cen- economic consequences of poverty
tral cities, suburbs, and combinations and further segregates the poor from
of these parts. As growth patterns and the middle and upper classes.
socioeconomic relationships among Demographer Douglas Massey pre-
the components of metropolitan areas dicts these trends will be self-perpetu-
change, definitions change. After each ating. The geographic distance and
decennial census, some metropolitan concentration of poverty will foster
areas in the United States are rede- the evolution of incompatible cul-
Suburban fined, usually by expanding them to tures, and it will be increasingly hard
areas are include adjacent counties. In 2000, for the poor and wealthy to interact
OMB introduced the term core based on the job, in the classroom, or in
growing more statistical areas (CBSA) to refer collec- social situations. William Julius Wilson
rapidly than tively to metropolitan and micropoli- suggests that the African American
tan statistical areas.60 poor in urban areas lost an important
central cities. In every metropolitan area, how- source of social and economic sup-
ever, suburban areas grow more port as middle- and upper-class blacks
rapidly than central cities. Many cen- moved out of central cities. This per-
tral cities, such as Philadelphia, have petuated the unemployment and
been losing population for several unstable family lives common among
decades, although some other U.S. blacks in low-income areas.63
cities bucked this trend and gained
population in the 1990s.61
Metropolitan areas grow outward
from original central cities, gobbling Population Growth
up additional cities and counties in
their paths. Los Angeles, for instance, Issues
has more incorporated cities within For most of human history, world popu-
its sprawl than do some states. lation never exceeded 10 million peo-
More recently, transportation and ple. The death rate was about as high as
communications advances, restructur- the birth rate, and the rate of popula-
ing of jobs, and other changes are tion growth was scarcely above zero.
transforming urban lifestyles, giving Significant population growth began
rise to colorful new terms to describe about 8000 B.C., when humans began
the new patterns, including: leapfrog to farm and raise animals (see Figure
development, reverse commuting, 10). By 1650, world population had
consumer cities, edge cities, and expanded about 50 times—from 10 mil-
boomburbs.62 lion to 500 million. Then world popula-
Population distribution and tion shot up another 500 million
redistribution affect the demographic people in just 150 years, reaching its
composition of the areas involved first billion around 1800. It achieved its
and can generate many social and second billion by 1930, 130 years later;
economic consequences. Heavy a third billion by 1960, only 30 years
migration into Florida from abroad later; and a fourth billion by 1975, just
and other states in the 1980s and 15 years later. But the last fifth and sixth
1990s not only moved that state from billion (attained in 1987 and 1999),
seventh to fourth place in population took just over a decade each. Although
rank but also fundamentally altered the pace of world population growth
the state’s age, racial, and ethnic has slowed, we still expect another bil-
composition. In many metropolitan lion added before 2015.
32
Figure 10
World Population Growth Through History
Billions of people
12 12

11 11
2100
10 10
Modern
9 Age 9

8 Old 8
Stone Bronze Iron Middle
Age New Stone Age Age Age Ages
7 7

6 2000 Future 6

5 5

4 1975 4

3 3
1950
2 2
1900
1 Black Death—the plague 1800 1

1+ million 7000 6000 5000 4000 3000 2000 1000 A.D. A.D. A.D. A.D. A.D. A.D.
years B.C. B.C. B.C. B.C. B.C. B.C. B.C. 1 1000 2000 3000 4000 5000

Sources: Population Reference Bureau; and United Nations, World Population Projections to 2100 (1998).

But the population explosion, as it often requires direct action by policy-

is often termed, is not just an awe- makers. Just slowing population
inspiring demographic phenomenon. growth cannot solve such problems,
It has many demographic and societal but it can contribute to their solution.
consequences, such as international
and internal migration and the emer-
gence of gigantic cities and shanty Demographic Transition
towns. While some analysts downplay The unprecedented growth of world
the negative impact of population population in the modern era arose
growth,64 many believe that popula- because births began to outnumber
tion growth multiplies the damage deaths. In ancient times, the birth rate
created by other world problems,65 and the death rate fluctuated around
degrading the environment, deplet- a relatively high level, and essentially
ing resources, and overwhelming gov- cancelled each other out. This formed
ernment institutions, national the first stage of a process described
economies, and all other resources. by the theory of the demographic
Population growth is not solely transition (see Figure 11, page 34).
responsible for these social problems. This theory evolved from the his-
Environmental degradation, for exam- tory of population growth in Europe
ple, is brought about not only by the and the United States and has been
number of people, but by how much applied to populations everywhere.
and what they consume. Poverty is In Stage 1 of the classic demo-
often produced by the uneven distrib- graphic transition, the death rate was
ution of income within a country, not extremely high because of poor
just by large numbers of people. Solv- health and harsh living conditions.
ing these social and economic ills Life expectancy at birth was less than
33
Figure 11 sal enemy: death. Social attitudes, such
The Classic Stages of Demographic Transition as the high value attached to having
many children, are slower to change. It
Birth/death rates
also takes time for people to recognize
Stage 1 Stage 2 Stage 3 Stage 4 that rapid population growth creates
pressures on food and land and that
the pressure can be eased by having
fewer children. It can take generations
Birth rate for people accustomed to high child-
hood mortality to recognize that low
mortality means that they no longer
Natural
increase
need to have eight children to ensure
that four will survive to adulthood.
In Stage 3 of the demographic
Death rate transition, the birth rate moves down-
ward, eventually catching up with the
death rate. Population growth remains
relatively high during the early part of
Time the third stage, but falls to near zero
in the later part.
Note: Natural increase or decrease is produced from the difference between the number of births In Stage 4 of the demographic tran-
and deaths.
sition, the birth rate and the death
rate are close together again, but they
30 years. If birth rates had not also fluctuate around a relatively low level.
been high, societies would simply have More developed countries in
died out—and many did! Europe and elsewhere have completed
The cultures in these societies the four stages of demographic transi-
encouraged high birth rates through tion. Most less developed nations are
religious teachings and social pres- still in Stage 2 or the early part of Stage
sure, essentially encouraging people 3 of the transition. Excluding China,
to “be fruitful and multiply.” Socially, a the growth rate for less developed
man’s virility and a woman’s status countries was 1.9 percent in 2003. If
often were linked to the number of growth were to continue at that rate,
children they had. But large families the population of these countries
also served a practical function in would double in less than 37 years.
these societies. Children furnished Will less developed countries even-
labor for family farms and supported tually complete the demographic tran-
elderly parents. Large families also sition to low fertility and mortality?
increased the economic, political, and They already have deviated from the
military power of their tribe or nation. path followed by Europe and the
Stage 2 of the demographic tran- United States. The importation of
sition began when the death rate medical supplies and technology
began to drop, probably because of caused death rates to plummet in
improved living conditions and health many parts of the less developed world
practices. The birth rate remained after World War II; in contrast, mortal-
high and may even have increased ity declines in Europe had occurred
because women were healthier. The slowly. The rapid decline in death
excess of births over deaths in the sec- rates, but not in birth rates, caused
ond stage of the transition ignited a unprecedented rates of natural
population explosion. increase in these countries beginning
Why didn’t the birth rate fall in tan- in the 1950s and accelerating in the
dem with the death rate? Most soci- 1960s. Growth slowed in many coun-
eties eagerly accept technological and tries in the 1980s and 1990s. Brazil,
medical innovations, as well as other Mexico, South Korea, and Thailand,
aspects of modernization, because of for example, experienced dramatic
their obvious utility against the univer- declines in birth rates. Fertility rates
34
dropped in many African countries as The global TFR will not fall to
well, but they are still high enough to replacement level immediately for
keep the region’s growth rate well two reasons. First, the fundamental
above 2 percent annually. social beliefs and cultural practices
Many demographers question that produce high fertility in many
whether Europe’s demographic transi- countries do not change quickly. Sec-
tion is a realistic model for less devel- ond, the world’s current age structure
oped countries in this century. Even if will generate massive growth even if a
all countries eventually undergo a relatively small family size becomes
demographic transition (and most the norm in the near future.
population experts assume they will), Almost one-third of the world’s
it is clear that individual countries are inhabitants are below age 15, and
following very different timetables and they inevitably will become the par-
paths for achieving it. The HIV/AIDS ents of the largest birth cohorts in his-
pandemic has derailed the transition tory. But, like any explosion, the
to low mortality in some areas, and no population explosion will eventually
one knows for how long. But the tim- fizzle, probably around the middle of
ing of fertility declines in less devel- this century. By then, the demo-
oped countries is probably the key to graphic transition will have run its
the ultimate size of the world’s popula- course in most countries of the world
tion. Population and policy experts and the world growth rate will proba-
debate just which actions or policies, bly be near zero. Recent estimates of
such as improving the educational lev- how large world population will actu-
els of women or making contraceptives ally be when it stops growing are in
easily available, will initiate declines in the 8.5 billion to 12 billion range.
the birth rate.66 Can the Earth support such huge
populations?68 As new technologies are
devised and as resource management
Future Prospects techniques are improved, the carrying
If the present rate of population capacity of the Earth expands, making
growth were to continue, world popu- it impossible to predict the ultimate
lation would rocket to 12 billion by number of people the world can sup-
2050, 24 billion by 2100, and so on. port. But many experts think that a
Humanity would outweigh the Earth world population of 10 billion may be
and then the solar system in a remark- the maximum that could be supported
ably short period of time if the present comfortably. Other scholars believe
growth rate continued indefinitely. But that the world’s basic biological sys-
no rate of growth can be sustained tems—its forests, grasslands, croplands,
indefinitely. A positive growth rate of and fisheries—and energy resources
+0.00001 ultimately would yield a cannot even support 10 billion. What-
population whose mass would expand ever the peak carrying capacity of the
at the speed of light, while a negative Earth, world population might stabilize
rate of -0.00001 ultimately would carry and remain uncomfortably close to
humanity back past Adam and Eve.67 that maximum level once population
Zero population growth, which growth has ceased. Or, world popula-
characterized human population for tion might decline to a lower, more
more than 99 percent of its history, manageable level for both humans and
must be achieved once again, at least the environment.
as a long-term average, if the human
species is to survive.
In order for world population Population Decline
growth to slow or stop (assuming that There is no homeostatic mechanism
mortality declines over the long that maintains a society at near zero
term), the global TFR would need to growth. Societies can easily slip into
drop from its present 2.8-child per population decline. Indeed, some
woman average to a 2-child average. population experts and interest
35
 groups would welcome such a popu- include the scarcity and waste of social
lation implosion. But zero growth or resources caused by baby booms and
population decline has its own prob- busts; premature death, especially in
lems. One is that the proportion of certain demographic subgroups; the
the population made up of older heavy concentration of population in
people rises dramatically. Older peo- some urban areas and depopulation
ple consume a disproportionate in rural areas; social disturbances
share of medical and other costly caused by changes in a population’s
public services. Labor force short- racial and ethnic composition; and
ages also may develop.69 If popula- the threat of declining quality of life
tion declines rapidly, severe social for present and future generations
and economic problems can result. because of world population growth.
Natural decrease (fewer births The damage such problems produce
than deaths) is already a reality in is indisputable.
Germany, Italy, Russia, Sweden, and Americans are somewhat interested
There is no most former Soviet republics. The in population problems. They have
mechanism that rate of decline is extremely slow, but very general opinions on such issues as
many European leaders fear that the desirability of population growth,
maintains zero their falling populations eventually the appropriate amount of immigra-
population will threaten their economies, their tion, and the “ideal” racial and ethnic
defense systems, and even their composition of the population. Intense
growth. national identities. concern about such issues flares up
Some European governments occasionally. In recent years, Americans
have tried various economic incen- have become concerned about the flow
tives to encourage couples to have of legal and illegal immigrants into the
more children, including housing United States. Polls have indicated that
benefits, stipends, and lengthy paid Americans strongly favor imposing lim-
maternity and paternity leaves. But itations on immigration and com-
these financial incentives are expen- pletely terminating illegal movements
sive for national governments, and into the country.71
they have not boosted birth rates Yet, most Americans do not view
enough to ward off population population issues as among our most
decline. Massive immigration is not serious social problems. Population
an acceptable solution to population problems lack the dramatic event—
decline in most countries either. the startling calamity or outrageous
European countries have imposed incident—that galvanizes attention
strict controls against immigration, and action. Rather, they develop
and some have encouraged immi- inconspicuously through the processes
grants to leave. Long-term popula- of birth, death, and migration.
tion decline appears inevitable for Experts often disagree about the
most of Europe, but it will occur very severity of population problems.
slowly.70 Were it not for high immi- Debate about population has been
gration levels, the United States also going on at least since Aristotle, who
would face population decline in the cautioned that populations could out-
21st century because of low mortality strip their subsistence base, leading to
and below-replacement fertility. poverty and social discord.72
Thomas Malthus reached a similar
conclusion in the late 18th century. He
argued that the natural consequences
Concern About of population growth are poverty and
misery because the population will
Population eventually exceed the food supply.
The reader no doubt has noticed that In the 19th century, Karl Marx and
many social problems emanate from Friedrich Engels rejected this Malthu-
the population processes of fertility, sian view. They blamed poverty not
mortality, and migration. These on the poor or on overpopulation,
36
but on the evils of social organization that the rate of growth—whether posi-
in capitalist societies. Overpopulation tive or negative—will continue until
in their view was a natural feature of people are standing on each other’s
capitalism, and it would not exist in shoulders or until no one is left.74
socialist societies because the latter Such expectations, however, underesti-
would provide enough resources for mate a society’s ability to solve prob-
each person. When resources were lems through social change.
scarce, the hard times would provide
the motivation to reduce family size.
Today, the debate over overpopu-
lation continues. Media articles on Conclusion
world population growth vacillate The study of population dynamics
from doomsday hysteria to compla- involves the interplay among the
cent unconcern, depending on three sources of population change:
which experts are used as a source. fertility, mortality, and migration.
Concern about environmental prob- These variables determine the most
lems has brought more attention to basic characteristics of a population,
the consequences of world popula- as well as its demographic future.
tion growth. Commitment to the The effects of demographic variables
environment is a deeply and widely extend far beyond the growth or
held value among Americans, decline in the number of people. As
according to Gallup research. This demographer Samuel Preston has so
commitment increasingly is being eloquently written:
extended to population issues.73 “The study of population offers some-
Expectations also play a role in thing for everyone: the daily dramas of sex
determining the level of public con- and death, politics and war; the interlac-
cern about population problems. For ings of individuals in all their collectivi-
example, when concern about a popu- ties; the confrontations of nature and
lation explosion or about depopula- civilization, [of] statistics and diaries,
tion flares up, people tend to believe [of] self-interest and altruism.” 75

37
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38
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39
 Suggested Resources
General Texts and References
Casper, Lynne M., and Suzanne M. Bianchi. Continuity and Change in the American
Family. Thousand Oaks, CA: Sage Publications, 2001.
Cohen, Joel E. How Many People Can the Earth Support? New York: W.W. Norton & Co.,
1995.
Farley, Reynolds, ed. State of the Union: America in the 1990s. Vols. 1 and 2. New York:
Russell Sage Foundation, 1995.
Haupt, Arthur, and Thomas T. Kane. Population Handbook, International Edition, 4th
ed. Washington, DC: Population Reference Bureau, 1998.
Katz, Bruce, and Robert E. Lang, eds. Redefining Urban and Suburban America: Evidence
From Census 2000. Washington, DC: Brookings Institution Press, 2003.
Siegel, Jacob S. ed., Applied Demography: Applications to Business, Government, Law, and
Public Policy. San Diego, CA: Academic Press, 2001.
Weeks, John R. Population: An Introduction to Concepts and Issues, 8th ed. Belmont, CA:
Wadsworth, 2002.

Websites
National Center for Health Statistics
www.cdc.gov/nchs/
Population Reference Bureau
www.prb.org
U.S. Census Bureau
www.census.gov

Selected Population Bulletins

U.S. Population Trends and Issues
Kent, Mary M., and Mark Mather. “What Drives U.S. Population Growth?” Vol. 57,
no. 4 (2002).
Riche, Martha Farnsworth. “America’s Diversity and Growth: Signposts for the 21st
Century.” Vol. 55, no. 2 (2000).
Migration/Immigration
Brockerhoff, Martin P., “An Urbanizing World.” Vol. 55, no. 3 (2000).
Martin, Philip, and Elizabeth Midgley. “Immigration: Shaping and Reshaping Amer-
ica.” Vol. 58, no. 2 (2003).
Martin, Philip, and Jonas Widgren. “International Migration: Facing the Challenge.”
Vol. 57, no. 1 (2002).
Family and Social Welfare
Bianchi, Suzanne M., and Lynne M. Casper. “American Families.” Vol. 55, no. 3
(2000).
Himes, Christine L. “Elderly Americans.” Vol. 56, no. 4 (2001).
Lichter, Daniel T., and Martha L. Crowley. “Poverty in America: Beyond Welfare
Reform.” Vol. 57, no. 2 (2002).
Pollard, Kelvin M., and William P. O’Hare, “America’s Racial and Ethnic Minorities.”
Vol. 54, no. 3 (1999).
World Population Trends and Issues
Ashford, Lori S. “New Population Policies: Advancing Women’s Health and Rights,”
Vol. 56, no. 1 (2001).
De Souza, Roger-Mark, John S. Williams, and Frederick A.B. Meyerson, “Critical
Links: Population, Health, and the Environment.” Vol. 58, no. 3 (2003).
O’Neill, Brian, and Deborah Balk, “World Population Futures.” Vol. 56, no. 3 (2001).

40
Related PRB Publications Recent Population
Bulletins
For more information on population trends and issues, here are several PRB Volume 58 (2003)
publications available in print and on our website. No. 3 Critical Links: Population,
Health, and the Environment,
2003 World Population Data Sheet by Roger-Mark De Souza, John S.
by Carl Haub, 2003 Williams, and Frederick A.B. Meyerson
PRB’s World Population Data Sheet contains the latest population estimates, projec-
tions, and other key indicators for 200 countries. (DS03ENG) $4.50 Also published in No. 2 Immigration: Shaping and
French and Spanish. Reshaping America, by Philip Mar-
tin and Elizabeth Midgley

No. 1 Population Dynamics in

Making the Link: Population, Health, and Environment Latin America, by Jorge A. Brea
by Jonathan G. Nash and Roger-Mark De Souza, 2002
This wallchart provides information and data on critical linkages between people Volume 57 (2002)
and the environment. Thirteen demographic, health, and environment indicators No. 4 What Drives U.S. Population
are given for 123 countries, six world regions, and the world as a whole. Accompany- Growth? by Mary M. Kent and Mark
ing text and graphics highlight trends in urbanization, population momentum, con- Mather
sumption levels, carbon dioxide emissions, changes in land use, and declining
availability of fresh water. (IDS02ENV) $4.50 Also published in French and Spanish. No. 3 Facing the HIV/AIDS Pan-
demic, by Peter Lamptey, Merywen
Wigley, Dara Carr, and Yvette Collymore
Government Spending in an Older America No. 2 Poverty in America: Beyond
by Ronald Lee and John Haaga, 2002 Welfare Reform, by Daniel T. Lichter
The population of the United States is getting older. Older people receive more in and Martha L. Crowley
public benefits and public spending on health care than they pay each year in taxes.
Public finances must be adapted to deal with a new demographic situation. This No. 1 International Migration:
issue of PRB Reports on America does not support specific reform proposals, but Facing the Challenge, by Philip
rather presents data and criteria for judging the alternatives. (ROA 3.1) Available Martin and Jonas Widgren
online at www.prb.org.
Volume 56 (2001)
No. 4 Elderly Americans, by Chris-
tine L. Himes
2002 Women of Our World
by Justine Sass and Lori Ashford, 2002 No. 3 World Population Futures,
While the last half-century has seen major gains in women's health, education, and by Brian O’Neill and Deborah Balk
rights, progress has been slow or uneven in many areas. Gender inequality, or dis-
parities between men and women, is still pronounced in the poorest regions and No. 2 First Glimpses From the
countries of the world. Being born female affects one's life chances in all societies, 2000 U.S. Census, by Mary M. Kent,
but the particular conditions facing women vary from one society to another. This Kelvin M. Pollard, John Haaga, and
data sheet catalogs the status of women in 168 countries, with a focus on demogra- Mark Mather
phy, reproductive health, education, economic status, and political leadership.
(IDS02WWENG) $4.50 Also published in French and Spanish. No. 1 New Population Policies:
Advancing Women’s Health and
Rights, by Lori S. Ashford

Volume 55 (2000)
No. 4 American Families,
by Suzanne M. Bianchi and
Lynne M. Casper

No. 3 An Urbanizing World,

by Martin P. Brockerhoff

No. 2 America’s Diversity and

To order PRB publications (discounts available): Growth: Signposts for the 21st Cen-
tury, by Martha Farnsworth Riche
Population Reference Bureau
1875 Connecticut Ave., NW, Suite 520 No. 1 Attaining Global Health:
Washington, DC 20009 Challenges and Opportunities,
Phone: 800-877-9881 by Scott C. Ratzan, Gary L. Filerman,
Fax: 202-328-3937 and John W. LeSar
E-mail: popref@prb.org
Website: www.prb.org

To read selected PRB publications, go to: www.prb.org

Population Reference Bureau
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