He has worked on asset pricing with Eugene Fama. They wrote a series of papers that cast doubt on the validity of the Capital Asset Pricing Model (CAPM), which posits that a stock's beta alone should explain its average return. These papers describe two factors above and beyond a stock's market beta which can explain differences in stock returns: market capitalization and "value".[3] They also offer evidence that a variety of patterns in average returns, often labeled as "anomalies" in past work, can be explained with their Fama–French three-factor model.[4]