Lecture 5: Inflation: Engineering Economy
Lecture 5: Inflation: Engineering Economy
Lecture 5: Inflation: Engineering Economy
Engineering Economy
7th edition
Leland Blank
Anthony Tarquin
LEARNING OUTCOMES
• Purchasing power is a good indicator for the real value of money (real
money)
• Increase in money supply (related very much with the interest rate dictated by
the central bank) - As the value of money decreases (because of its
abundancy), it takes more money for the same amount of goods or services.
• Reduce or stagnant productivity i.e. constant amount of money, less goods
Constant Value Dollar
The money that maintain its value over time i.e represents the same
purchasing power over time.
Constant Value (Real Dollar) Actual Dollar
Year RM
0 RM 100 RM 100
1 RM 100 RM 100 (1+0.05)
2 RM 100 RM 100 (1+0.05)2
Money in one period of time t1, can be brought to the same value as
money in another period of time t2 by using;
𝑎𝑚𝑜𝑢𝑛𝑡 𝑖𝑛 𝑝𝑒𝑟𝑖𝑜𝑑 𝑡2
𝐴𝑚𝑜𝑢𝑛𝑡 𝑖𝑛 𝑝𝑒𝑟𝑖𝑜𝑑 𝑡1 = (𝐄𝐪. 𝟏)
𝑖𝑛𝑓𝑙𝑎𝑡𝑖𝑜𝑛 𝑟𝑎𝑡𝑒 𝑏𝑒𝑡𝑤𝑒𝑒𝑛 𝑡1 𝑎𝑛𝑑 𝑡2
𝐹𝑢𝑡𝑢𝑟𝑒 𝐷𝑜𝑙𝑙𝑎𝑟𝑠
𝐶𝑜𝑛𝑠𝑡𝑎𝑛𝑡 𝑉𝑎𝑙𝑢𝑒 𝐷𝑜𝑙𝑙𝑎𝑟𝑠 = 𝑡
(𝐄𝐪. 𝟐)
(1 + 𝑓)
𝑭𝑽 = 𝑷𝑽(𝟏 + 𝒓)𝒕
Three Different Interest Rates
► Real accumulation of wealth or interest rate i – Rate at which
interest is earned when effects of inflation are removed; i represents
the real increase in purchasing power
Note: This calculation only accounts for the decreased purchasing power
of the currency. It does not take into account the time value of money
(to be discussed)
Example: Market vs. Real Rate
Money in a medium-risk investment makes a guaranteed 8% per
year. Inflation rate has averaged 5.5% per year. What is the real
rate of return on the investment?
Solution
Solve for the real rate i in relation for if
if = i + f + (i)(f)
𝑖𝑓 − 𝑓 0.08 − 0.055
𝑖= =
1+𝑓 1 + 0.055
𝑖 = 0.024 = 2.4%
Two GENERAL ways to work problems when considering
inflation:
(1) Convert to constant value (CV) dollars, then use real rate i.
If f = inflation rate (% per year), the equation is:
Constant-value dollars = future dollars = then-current dollars
(1+ f)t (1+ f)t
(2) Leave money amounts as is and use market rate (interest rate
adjusted for inflation), if
if = i + f + (i)(f)
PW Calculations with Inflation
Two ways to account for inflation in PW calculations
(1) Convert cash flow into constant-value (CV) dollars and use regular i
where: CV = future dollars/(1 + f)t = then-current dollars/(1 + f)t
f = inflation rate
(Note: Calculations up to now have assumed constant-value dollars)
(2) Express cash flow in future (then-current ) dollars and use market
interest rate where if = i + f + (i)(f)
Example: PW with Inflation
A honing machine will have a cost of $25,000 (future cost) six years from
now. Find the PW of the machine, if the real interest rate is 10% per year
and the inflation rate is 5% per year using (a) constant-value dollars,
and (b) future dollars.
Solution:
(a) The amount accumulated is a function of the market interest rate, if
if = 0.08 + 0.05 + (0.08)(0.05) = 13.4%
(d) In order to maintain purchasing power and earn a real return, money must
grow by the inflation rate and the interest rate, or if = 13.4%, as in part (a)
FW = 15,000(F/P,13.4%,10)
= $52,750
AW (Capital Recovery) with Inflation
The A/P and A/F factors require the use of if when inflation is considered
A = -180,000(A/P,12.27%,5) - 70,000(P/F,12.27%,3)(A/P,12.27%,5)
= -180,000(0.27927) - 70,000(0.70666)(0.27927)
= $-64,083 per year