Jensen's alpha was first used as a measure in the evaluation of mutual fund managers by Michael Jensen in 1968.[2] The CAPM return is supposed to be 'risk adjusted', which means it takes account of the relative riskiness of the asset.
This is based on the concept that riskier assets should have higher expected returns than less risky assets. If an asset's return is even higher than the risk adjusted return, that asset is said to have "positive alpha" or "abnormal returns". Investors are constantly seeking investments that have higher alpha.
Since Eugene Fama, many academics believe financial markets are too efficient to allow for repeatedly earning positive Alpha, unless by chance. To the contrary, empirical studies of mutual funds spearheaded by Russ Wermers usually confirm managers' stock-picking talent[citation needed], finding positive Alpha, however this work has been criticized. Among the criticisms is survivorship bias.
Nevertheless, Alpha is still widely used to evaluate mutual fund and portfolio manager performance, often in conjunction with the Sharpe ratio and the Treynor ratio.