financial,  invested  in  the  firm.  In  this  chapter,  we  will  argue  that  risk  in  an  equity 
investment has to be perceived through the eyes of investors in the firm. Since firms like 
Disney often have thousands of investors, often with very different perspectives, we will 
go further. We will assert  that risk has to  be measured from the perspective of not just 
any investor in the stock, but of the marginal investor, defined to be the investor most 
likely to  be trading on the  stock at any  given point  in  time.  The  objective in  corporate 
finance is the maximization of firm value and stock price. If we want to stay true to this 
objective, we have to consider the viewpoint of those who set the stock prices, and they 
are the marginal investors.  
Finally, the risk in a company can be viewed very differently by investors in its 
stock  (equity  investors)  and  by  lenders  to  the  firm  (bondholders  and  bankers).  Equity 
investors  who  benefit  from  upside  as  well  as  downside  tend  to  take  a  much  more 
sanguine  view  of  risk  than  lenders  who  have  limited  upside  but  potentially  high 
downside. We will consider how to measure equity risk in the first part of the chapter and 
risk from the perspective of lenders in the latter half of the chapter. 
  We will be presenting a number of different risk and return models in this chapter. 
In  order  to  evaluate  the  relative  strengths  of  these  models,  it  is  worth  reviewing  the 
characteristics of a good risk and return model.  
1. It should come up with a measure of risk that  applies to all assets and not be 
asset-specific. 
2.  It  should clearly  delineate what types  of  risk  are  rewarded and  what are  not, 
and provide a rationale for the delineation. 
3. It should come up with standardized risk measures, i.e., an investor presented 
with  a  risk measure  for  an  individual  asset  should  be  able  to  draw  conclusions 
about whether the asset is above-average or below-average risk. 
4.  It  should  translate  the  measure  of  risk  into  a  rate  of  return  that  the  investor 
should demand as compensation for bearing the risk. 
5. It should work well not only at explaining past returns, but also in predicting 
future expected returns.