Capital Asset Pricing Model (CAPM) and the Single Index Model (SIM) are single factor models whose only risk factor is the market portfolio’s return. Say a Taxi company and an Umbrella company are influenced by two factors, the market portfolio return and rainfall. When it rains, both the Taxi and Umbrella companies’ stock prices do well. When there’s no rain, both do poorly. Assume that rainfall risk is a systematic risk that cannot be diversified and that rainfall has zero correlation with the market portfolio’s returns.
Which of the following statements about these two stocks is NOT correct?
The CAPM and SIM: