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9.understanding Risk

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Understanding Risk

McGraw-Hill/Irwin Copyright © 2008 by The McGraw-Hill Companies, Inc. All rights reserved.
Risk: Definition

Risk is a measure of _________ about the


future payoff of an investment,
measured over some time horizon and
relative to a benchmark.
Measuring Risk

1. List of all possible outcomes


2. List the __________ of each occurring
Measuring Risk
Example: Single Coin Toss

Lists all possibilities, one of them must occur.


Probabilities sum to _______.
Measuring Risk:
Case 1
Investing $1000

Possibilities Probability Payoff

1 0.5 $700

2 0.5 $1400

(Two possibilities are equally likely)


Measuring Risk:
Case 2
Investing $1000

Possibilities Probability Payoff


1 0.1 $100
2 0.4 $700
3 0.4 $1,400
4 0.1 $2,000
Measuring Risk:
Comparing Cases 1 & 2
• What is the Expected value in both the cases?

• Is the risk the same?


Measuring Risk:
Variance & Standard Deviation
• Variance:
Average of squared deviation of the
outcomes from the expected value, weighted
by the probabilities.

• Standard Deviation:
Square root of the variance
(Same units as the payoff)
Measuring Risk:
Comparing Cases 1 & 2
Case 1: Standard Deviation =$350
Case 2: Standard Deviation =$528

The greater the standard deviation, the


________ the risk.
Leverage
• Leverage:
Borrowing to finance part of an investment
Leverage _________ Expected return and risk.
• Invest
– $1000 or your own + $1000 borrowed
– Expected return doubles
– Standard Deviation doubles
Risk-Return Tradeoff

More risk  Bigger risk premium  Higher expected return

Risk Requires Compensation


Reducing Risk through Diversification
Two ways to diversify your investments. You can

1. hedge risks

2. spread them among the many investments.


Reducing Risk:
Hedging
Compare:
1. Invest $100 in GE
2. Invest $100 in Texaco
3. Invest ½ in each:
$50 in GE
+ $50 in Texaco
Reducing Risk:
Hedging
Initial investment= $100

Hedging has eliminated the risk entirely.


Reducing Risk:
Spreading
• You can’t always hedge
• The alternative is to spread risk around
• Find investments whose payoffs
are unrelated
Reducing Risk:
Spreading
Consider three investment strategies:
1. GE only,
2. Microsoft only, and
3. ½ in GE + ½ in Microsoft.
Reducing Risk:
Spreading

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