美联储：美国共同基金行业的技能和效率（英文版）

We propose a new measure of mutual fund manager ability: “efficiency” is the ability to accrue the risk premium associated with a risk factor. The familiar abnormal return, or alpha, is shown to be the sum of two distinct measures of ability: “aggregate efficiency” which is the beta-weighted sum of the fund’s (in)efficiencies across risk factors, and “skill,” the component that is unrelated to factor exposures. Using a panel of U.S. equity mutual fund returns from 1999-2023, we document signi