An empirical q-factor model consisting of the market factor, a size factor, an investment factor, and a profitability factor largely summarizes the cross section of average stock returns. A comprehensive examination of nearly 80 anomalies reveals that about one-half of the anomalies are insignificant in the broad cross section. More importantly, with a few exceptions, the q-factor model's performance is at least comparable to, and in many cases better than that of the Fama-French (1993) 3-factor model and the Carhart (1997) 4-factor model in capturing the remaining significant anomalies.

This paper is a new incarnation of the defunct work previously circulated under the titles "Neoclassical Factors," "An equilibrium three-factor model," "Production-based factors," "A better three-factor model that explains more anomalies," and "An alternative three-factor model." We are extremely grateful to Robert Novy-Marx