The neoclassical theory of investment has mainly been tested with physical investment, but we show that it also helps explain intangible investment. At the firm level, Tobin’s q explains physical and intangible investment roughly equally well, and it explains total investment even better. Compared with physical capital, intangible capital adjusts more slowly to changes in investment opportunities. The classic q theory performs better in firms and years with more intangible capital: Total and even physical investment are better explained by Tobin’s q and are less sensitive to cash flow. At the macro level, Tobin’s q explains intangible investment many times better than physical investment. We propose a simple, new Tobin’s q proxy that accounts for intangible capital, and we show that it is a superior proxy for both physical and intangible investment opportunities.

We model 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 and performance is stronger than the cross‐sectional relation, as the model predicts. Also as predicted, the turnover‐performance relation is stronger for funds trading less‐liquid stocks and funds likely to possess greater skill. Turnover is correlated across funds. The common component of turnover is positively correlated with proxies for stock mispricing. Turnover of similar funds helps predict a fund's performance.