Introduction to Corporate Finance

Ross et al.: Fundamentals

of Corporate Finance, Sixth

Edition, Alternate Edition

V. Risk and Return 13. Return, Risk, and the

Security Market Line

© The McGraw−Hill^465

Companies, 2002

Another way of seeing that A offers a superior return for its level of risk is to note
that the slope of our line for Asset B is:

Slope 

6.67%

Thus, Asset B has a reward-to-risk ratio of 6.67 percent, which is less than the 7.5 per-
centoffered by Asset A.

The Fundamental Result The situation we have described for Assets A and B could
not persist in a well-organized, active market, because investors would be attracted to
Asset A and away from Asset B. As a result, Asset A’s price would rise and Asset B’s
price would fall. Because prices and returns move in opposite directions, A’s expected
return would decline and B’s would rise.
This buying and selling would continue until the two assets plotted on exactly the
same line, which means they would offer the same reward for bearing risk. In other
words, in an active, competitive market, we must have the situation that:



This is the fundamental relationship between risk and return.
Our basic argument can be extended to more than just two assets. In fact, no matter
how many assets we had, we would always reach the same conclusion:

The reward-to-risk ratio must be the same for all the assets in the market.

E(RB) 
Rf

(^) B
E(RA)
Rf
(^) A

16%
8%

1.2

E(RB) 
Rf

(^) B
CHAPTER 13 Return, Risk, and the Security Market Line 437

FIGURE 13.2C

Portfolio beta

( (^) P)
Portfolio expected
return (E(RP))
E(RB) = 16%
1.2 =
Rf = 8%
= 6.67%
E(RA) = 20%
= 7.50%
1.6 =
Asset A
Asset B
(^) B (^) A
Portfolio Expected Returns and Betas for Both Assets