Recent studies link mutual fund performance to measures of active management, and this evidence often takes the form of large spreads in unconditional alphas for characteristic-sorted portfolios. Unconditional benchmarks can, however, produce misleading inferences on managerial skill for strategies that exhibit substantial turnover and unstable factor exposures. We propose a performance attribution model that accounts for predictable changes in portfolio style. Compared to existing methods, our benchmarks yield superior tracking performance and a more powerful statistical assessment of abnormal returns. We re-evaluate six active management proxies using our method and conclude that these measures are largely unrelated to managerial ability.