The Capital Asset Pricing Model (CAPM) has far-reaching practical implications for both investors and corporate managers. The model implies that the market portfolio is mean variance efficient, and thus advocates passive investment. It also provides the most widely used measure of risk, beta,...

Numerous studies have examined the mean/variance efficiency of various market proxies by employing sample parameters and have concluded that these proxies are inefficient. These findings cast doubt about the capital asset pricing model (CAPM), one of the cornerstones of modern finance. This...