ABSTRACT We show that corporate investment decisions can explain the conditional dynamics in expected asset returns. Our approach is similar in spirit to Berk, Green, and Naik (1999) , but we introduce to the investment problem operating leverage, reversible real options, fixed adjustment costs, and finite growth opportunities. Asset betas vary over time with historical investment decisions and the current product market demand. Book‐to‐market effects emerge and relate to operating leverage, while size captures the residual importance of growth options relative to assets in place. We estimate and test the model using simulation methods and reproduce portfolio excess returns comparable to the data.

We examine the form, adoption rates, and economic rationale for various mutual fund investment restrictions. A sample of U.S. domestic equity funds from 1994 to 2000 reveals systematic patterns in investment constraints, consistent with an optimal contracting equilibrium in the fund industry. Restrictions are more common when (i) boards contain a higher proportion of inside directors, (ii) the portfolio manager is more experienced, (iii) the fund is managed by a team rather than an individual, and (iv) the fund does not belong to a large organizational complex. Low- and high-constraint funds produce similar risk-adjusted returns, also consistent with an optimal contracting equilibrium.