Covariance and Correlation
-Portfolio risk depends on the correlation between the returns of the assets in the portfolio
-Covariance and the correlation coefficient provide a measure of the returns on two assets to vary
Two Asset Portfolio Return – Stock and Bond
Covariance and Correlation Coefficient
Correlation Coefficients: Possible Values
Range of values for r 1,2
-1.0 < r < 1.0
If r = 1.0, the securities would be perfectly positively correlated (meaning two assets move in the same direction)
If r = - 1.0, the securities would be perfectly negatively correlated (meaning two assets move in the opposite direction)
Two Asset Portfolio St Dev – Stock and Bond
In General, For an n-Security Portfolio:
rp = Weighted average of the
n securities
sp2 = (Consider all pair-wise
covariance measures)
Three Rules of Two-Risky-Asset Portfolios
Numerical Example: Bond and Stock Returns
Returns
Bond = 6% Stock = 10%
Standard Deviation
Bond = 12% Stock = 25%
Weights
Bond = .5 Stock = .5
Correlation Coefficient
(Bonds and Stock) = 0
Return = 8%
.5(6) + .5 (10)
Standard Deviation = 13.87%
[(.5)^2 (12)^2 + (.5)^2 (25)^2 + …
2 (.5) (.5) (12) (25) (0)]^ ½
[192.25]^ ½ = 13.87
Investment Opportunity Set for Stocks and Bonds
Investment Opportunity Set for Stocks and Bonds with Various Correlations
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