During the past few decades, the fraction of the equity market owned directly by individuals declined significantly. The same period witnessed investment trends that include the growth of indexing as well as shifts by active managers toward lower fees and more index-like investing. I develop an...

We empirically analyze the nature of returns to scale in active mutual fund management. We find strong evidence of decreasing returns at the industry level: As the size of the active mutual fund industry increases, a fund's ability to outperform passive benchmarks declines. At the fund level,...

We model optimal fund turnover in the presence of time-varying profit opportunities. Our model predicts a positive relation between an active fund's turnover and its subsequent benchmark-adjusted return. We find such a relation for equity mutual funds. This time-series relation between turnover...

We argue that active management's popularity is not puzzling despite the industry's poor track record. Our explanation features decreasing returns to scale: As the industry's size increases, every manager's ability to outperform passive benchmarks declines. The poor track record occurred before...

We study tradeoffs among active mutual funds' characteristics. In both our equilibrium model and the data, funds with larger size, lower expense ratio, and higher turnover hold more-liquid portfolios. Portfolio liquidity, a concept introduced here, depends not only on the liquidity of the...