Investments

1
Risk and Risk AversionBKM Ch 6

• Zvi Wiener
• tel [phone] mswiener_at_mscc.huji.ac.il

2
Risk - Uncertain Outcomes
W1 150 Profit 50
p 60
W 100
1-p 40
W2 80 Profit -20
E(W) pW1 (1-p)W2 6 (150) .4(80) 122 s2
pW1 - E(W)2 (1-p) W2 - E(W)2 .6
(150-122)2 .4(80122)2 1,176,000 s 34.293
3
Risky Investments with Risk-Free Investment
W1 150 Profit 50
p .6
Risky Inv.
1-p .4
100
W2 80 Profit -20
Risk Free T-bills
Profit 5
Risk Premium 17
4
Risk Aversion Utility

• Investors view of risk
• Risk Averse
• Risk Neutral
• Risk Seeking
• Utility
• Utility Function
• U E ( r ) - .005 A s 2
• A measures the degree of risk aversion

5
Risk Aversion and Value Using the Sample
Investment

• U E ( r ) - .005 A s 2
• .22 - .005 A (34) 2
• Risk Aversion A Value
• High 5 -6.90
• 3 4.66
• Low 1 16.22

T-bill 5
6
Dominance Principle
Expected Return
4
2
3
1
Variance or Standard Deviation
2 dominates 1 has a higher return 2
dominates 3 has a lower risk 4 dominates 3
has a higher return
7
Utility and Indifference Curves

• Represent an investors willingness to trade-off
  return and risk.
• Example
• Exp Ret St Deviation UE ( r ) - .005As2
• 10 20.0 2
• 15 25.5 2
• 20 30.0 2
• 25 33.9 2

8
Indifference Curves
Expected Return
Increasing Utility
Standard Deviation
9
Expected Return

• Rule 1 The return for an asset is the
  probability weighted average return in all
  scenarios.

10
Variance of Return

• Rule 2 The variance of an assets return is the
  expected value of the squared deviations from the
  expected return.

11
Return on a Portfolio

• Rule 3 The rate of return on a portfolio is a
  weighted average of the rates of return of each
  asset comprising the portfolio, with the
  portfolio proportions as weights.
• rp W1r1 W2r2
• W1 Proportion of funds in Security 1
• W2 Proportion of funds in Security 2
• r1 Expected return on Security 1
• r2 Expected return on Security 2

12
Portfolio Risk with Risk-Free Asset

• Rule 4 When a risky asset is combined with a
  risk-free asset, the portfolio standard deviation
  equals the risky assets standard deviation
  multiplied by the portfolio proportion invested
  in the risky asset.

13
Portfolio Risk

• Rule 5 When two risky assets with variances s12
  and s22, respectively, are combined into a
  portfolio with portfolio weights w1 and w2,
  respectively, the portfolio variance is given by
• ?p2 w12?12 w22?22 2W1W2 Cov(r1r2)
• Cov(r1r2) Covariance of returns for
• Security 1 and Security 2

14
Home Assignment

• Required
  problems 1, 2, 3, 4, (3rd
  ed).
• problems 1, 2, 3, 4, (5th ed).
• Appendix b1 submit !
• closely follow financial news!