In: Finance
The risk premium is the market return minus the risk free return
(treasury bill rate)
12%-4%= 8%.
The Capital Asset pricing model says the expected return on a stock
is equal to the risk free rate plus beta times the difference
between the expected market return and the risk free return. Beta
is a measure of the risk of the individual stock you get by running
a linear regression on the returns of the individual stock versus
the returns of the market.
So here we have R= 4 + 1.5(12-4)= 4+12=16% expected return on the
stock.
If the expected return on the stock is 9.8 we have
9.8= 4 +.8(x-4)
9.8= 4+ .8x- 3.2
.8x=9
x=11.25 since this is less than the market return of 12% we would
expect the stock to have a negative NPV.
If the stock has an expected return of 11.2 we have
11.2= 4 +B(12-4)
8B= 7.2
B= 0.9
The investor could do better by, say, putting 40% of his portfolio
in T-bills and 60% in an index fund. This would have an expected
return of .4(6) +.6(12)= 9.6, which would be better than the bonds,
but have less risk due to the T-bills which are risk free.
You wouldn't want to put your money in two investments that are
perfectly correlated (+1). This increases rather than decreases the
risk. You want negative correlation which will reduce the
volatility of the portfolio and thus the risk.