In: Statistics and Probability
In this exercise, we examine the effect of combining investments
with positively correlated risks, negatively correlated risks, and
uncorrelated risks. A firm is considering a portfolio of assets.
The
portfolio is comprised of two assets, which we will call ''A" and
"B." Let X denote the annual rate of return from asset A in the
following year, and let Y denote the annual rate of return from
asset B in the following year. Suppose that
E(X) = 0.15 and E(Y) = 0.20,
SD(X) = 0.05 and SD(Y) = 0.06,
and CORR(X, Y) = 0.30.
(a) What is the expected return of investing 50% of the portfolio
in asset A and 50% of the portfolio in asset B? What is the
standard deviation of this return?
(b) Replace CORR(X, Y) = 0.30 by CORR(X, Y) = 0.60 and answer the
questions in part (a). Do the same for CORR(X, Y) = 0.60, 0.30, and
0.0.
(c) (Spreadsheet Exercise). Use a spreadsheet to perform the
following analysis. Suppose that the fraction of the portfolio that
is invested in asset B is f, and so the fraction of the portfolio
that is invested in asset A is (1 f). Letting f vary from f = 0.0
to f = 1.0 in increments of 5% (that is, f = 0.0, 0.05, 0.10, 0.15,
. . . ), compute the mean and the standard deviation of the annual
rate of return of the portfolio (using the original data for the
problem). Notice that the expected return of the portfolio varies
(linearly) from 0.15 to 0.20, and the standard deviation of the
return varies (non-linearly) from 0.05 to 0.06. Construct a chart
plotting the standard deviation as a function of the expected
return.
(d) (Spreadsheet Exercise). Perform the same analysis as in part
(c) with CORR (X, Y) = 0.30 replaced by CORR(X, Y) = 0.60, 0.0,
0.30, and 0.60.
a)
E(X) | 0.15 | sd(X) | 0.05 |
E(Y) | 0.2 | sd(Y) | 0.06 |
r | 0.3 | ||
a) | |||
expected return | 0.175 | ||
sd | 0.044441 |
formula
E(X) | 0.15 | sd(X) | 0.05 |
E(Y) | 0.2 | sd(Y) | 0.06 |
r | 0.3 | ||
expected return | =0.5*B1+0.5*B2 | ||
sd | =SQRT(0.5^2 * D1^2 + 0.5^2 * D2^2 + 2* 0.5 *0.5 * B4*D1*D2) |
b)
r | 0.6 |
expected return | 0.175 |
sd | 0.049244289 |
r | 0 |
expected return | 0.175 |
sd | 0.039051248 |
c)
w1 | w2 | mean | sd |
0 | 1 | 0.2 | 0.06 |
0.05 | 0.95 | 0.1975 | 0.057799 |
0.1 | 0.9 | 0.195 | 0.055705 |
0.15 | 0.85 | 0.1925 | 0.053728 |
0.2 | 0.8 | 0.19 | 0.051884 |
0.25 | 0.75 | 0.1875 | 0.050187 |
0.3 | 0.7 | 0.185 | 0.048652 |
0.35 | 0.65 | 0.1825 | 0.047294 |
0.4 | 0.6 | 0.18 | 0.04613 |
0.45 | 0.55 | 0.1775 | 0.045175 |
0.5 | 0.5 | 0.175 | 0.044441 |
0.55 | 0.45 | 0.1725 | 0.04394 |
0.6 | 0.4 | 0.17 | 0.043681 |
0.65 | 0.35 | 0.1675 | 0.043666 |
0.7 | 0.3 | 0.165 | 0.043898 |
0.75 | 0.25 | 0.1625 | 0.044371 |
0.8 | 0.2 | 0.16 | 0.045078 |
0.85 | 0.15 | 0.1575 | 0.046008 |
0.9 | 0.1 | 0.155 | 0.047149 |
0.95 | 0.05 | 0.1525 | 0.048485 |
1 | 0 | 0.15 | 0.05 |
formula
E(X) | 0.15 | sd(X) | 0.05 |
E(Y) | 0.2 | sd(Y) | 0.06 |
r = 0.3 | |||
w1 | w2 | mean | sd |
0 | =1-A6 | =A6*$B$1+B6*$B$2 | =SQRT(A6^2*$D$1^2 + B6^2 *$D$2^2+ 2*A6*B6*0.3*$D$1*$D$2) |
=0.05+A6 | =1-A7 | =A7*$B$1+B7*$B$2 | =SQRT(A7^2*$D$1^2 + B7^2 *$D$2^2+ 2*A7*B7*0.3*$D$1*$D$2) |
=0.05+A7 | =1-A8 | =A8*$B$1+B8*$B$2 | =SQRT(A8^2*$D$1^2 + B8^2 *$D$2^2+ 2*A8*B8*0.3*$D$1*$D$2) |
=0.05+A8 | =1-A9 | =A9*$B$1+B9*$B$2 | =SQRT(A9^2*$D$1^2 + B9^2 *$D$2^2+ 2*A9*B9*0.3*$D$1*$D$2) |
=0.05+A9 | =1-A10 | =A10*$B$1+B10*$B$2 | =SQRT(A10^2*$D$1^2 + B10^2 *$D$2^2+ 2*A10*B10*0.3*$D$1*$D$2) |
=0.05+A10 | =1-A11 | =A11*$B$1+B11*$B$2 | =SQRT(A11^2*$D$1^2 + B11^2 *$D$2^2+ 2*A11*B11*0.3*$D$1*$D$2) |
=0.05+A11 | =1-A12 | =A12*$B$1+B12*$B$2 | =SQRT(A12^2*$D$1^2 + B12^2 *$D$2^2+ 2*A12*B12*0.3*$D$1*$D$2) |
=0.05+A12 | =1-A13 | =A13*$B$1+B13*$B$2 | =SQRT(A13^2*$D$1^2 + B13^2 *$D$2^2+ 2*A13*B13*0.3*$D$1*$D$2) |
=0.05+A13 | =1-A14 | =A14*$B$1+B14*$B$2 | =SQRT(A14^2*$D$1^2 + B14^2 *$D$2^2+ 2*A14*B14*0.3*$D$1*$D$2) |
=0.05+A14 | =1-A15 | =A15*$B$1+B15*$B$2 | =SQRT(A15^2*$D$1^2 + B15^2 *$D$2^2+ 2*A15*B15*0.3*$D$1*$D$2) |
=0.05+A15 | =1-A16 | =A16*$B$1+B16*$B$2 | =SQRT(A16^2*$D$1^2 + B16^2 *$D$2^2+ 2*A16*B16*0.3*$D$1*$D$2) |
=0.05+A16 | =1-A17 | =A17*$B$1+B17*$B$2 | =SQRT(A17^2*$D$1^2 + B17^2 *$D$2^2+ 2*A17*B17*0.3*$D$1*$D$2) |
=0.05+A17 | =1-A18 | =A18*$B$1+B18*$B$2 | =SQRT(A18^2*$D$1^2 + B18^2 *$D$2^2+ 2*A18*B18*0.3*$D$1*$D$2) |
=0.05+A18 | =1-A19 | =A19*$B$1+B19*$B$2 | =SQRT(A19^2*$D$1^2 + B19^2 *$D$2^2+ 2*A19*B19*0.3*$D$1*$D$2) |
=0.05+A19 | =1-A20 | =A20*$B$1+B20*$B$2 | =SQRT(A20^2*$D$1^2 + B20^2 *$D$2^2+ 2*A20*B20*0.3*$D$1*$D$2) |
=0.05+A20 | =1-A21 | =A21*$B$1+B21*$B$2 | =SQRT(A21^2*$D$1^2 + B21^2 *$D$2^2+ 2*A21*B21*0.3*$D$1*$D$2) |
=0.05+A21 | =1-A22 | =A22*$B$1+B22*$B$2 | =SQRT(A22^2*$D$1^2 + B22^2 *$D$2^2+ 2*A22*B22*0.3*$D$1*$D$2) |
=0.05+A22 | =1-A23 | =A23*$B$1+B23*$B$2 | =SQRT(A23^2*$D$1^2 + B23^2 *$D$2^2+ 2*A23*B23*0.3*$D$1*$D$2) |
=0.05+A23 | =1-A24 | =A24*$B$1+B24*$B$2 | =SQRT(A24^2*$D$1^2 + B24^2 *$D$2^2+ 2*A24*B24*0.3*$D$1*$D$2) |
=0.05+A24 | =1-A25 | =A25*$B$1+B25*$B$2 | =SQRT(A25^2*$D$1^2 + B25^2 *$D$2^2+ 2*A25*B25*0.3*$D$1*$D$2) |
=0.05+A25 | =1-A26 | =A26*$B$1+B26*$B$2 | =SQRT(A26^2*$D$1^2 + B26^2 *$D$2^2+ 2*A26*B26*0.3*$D$1*$D$2) |
d)
r | 0 | ||
w1 | w2 | mean | sd |
0 | 1 | 0.2 | 0.06 |
0.05 | 0.95 | 0.1975 | 0.057054798 |
0.1 | 0.9 | 0.195 | 0.054230987 |
0.15 | 0.85 | 0.1925 | 0.051548521 |
0.2 | 0.8 | 0.19 | 0.049030603 |
0.25 | 0.75 | 0.1875 | 0.046703854 |
0.3 | 0.7 | 0.185 | 0.044598206 |
0.35 | 0.65 | 0.1825 | 0.042746345 |
0.4 | 0.6 | 0.18 | 0.041182521 |
0.45 | 0.55 | 0.1775 | 0.039940581 |
0.5 | 0.5 | 0.175 | 0.039051248 |
0.55 | 0.45 | 0.1725 | 0.038538941 |
0.6 | 0.4 | 0.17 | 0.038418745 |
0.65 | 0.35 | 0.1675 | 0.038694315 |
0.7 | 0.3 | 0.165 | 0.039357337 |
0.75 | 0.25 | 0.1625 | 0.040388736 |
0.8 | 0.2 | 0.16 | 0.041761226 |
0.85 | 0.15 | 0.1575 | 0.043442491 |
0.9 | 0.1 | 0.155 | 0.045398238 |
0.95 | 0.05 | 0.1525 | 0.047594643 |
1 | 0 | 0.15 | 0.05 |
r | 0.6 | ||
w1 | w2 | mean | sd |
0 | 1 | 0.2 | 0.06 |
0.05 | 0.95 | 0.1975 | 0.058534178 |
0.1 | 0.9 | 0.195 | 0.057140179 |
0.15 | 0.85 | 0.1925 | 0.055823382 |
0.2 | 0.8 | 0.19 | 0.054589376 |
0.25 | 0.75 | 0.1875 | 0.053443896 |
0.3 | 0.7 | 0.185 | 0.052392748 |
0.35 | 0.65 | 0.1825 | 0.051441715 |
0.4 | 0.6 | 0.18 | 0.050596443 |
0.45 | 0.55 | 0.1775 | 0.04986231 |
0.5 | 0.5 | 0.175 | 0.049244289 |
0.55 | 0.45 | 0.1725 | 0.048746795 |
0.6 | 0.4 | 0.17 | 0.048373546 |
0.65 | 0.35 | 0.1675 | 0.048127435 |
0.7 | 0.3 | 0.165 | 0.048010416 |
0.75 | 0.25 | 0.1625 | 0.048023432 |
0.8 | 0.2 | 0.16 | 0.048166378 |
0.85 | 0.15 | 0.1575 | 0.048438105 |
0.9 | 0.1 | 0.155 | 0.048836462 |
0.95 | 0.05 | 0.1525 | 0.049358383 |
1 | 0 | 0.15 | 0.05 |