This article evaluates out-of-sample portfolio performance for a real-time investor who can exploit time variation in the conditional mean and volatility of stock returns in optimizing a multiperiod portfolio choice problem. With the presence of parameter uncertainty, our out-of-sample analysis shows that ignoring time variation in the first two return moments leads to significant utility costs of at least 1.97% of annualized certainty equivalent return. Accounting for the time-varying risk premium plays a more important role than considering time-varying volatility in improving portfolio performance. Interestingly, behaving myopically or ignoring the hedge against changes in future investment opportunities can lead to small out-of-sample utility losses or even utility gains.

This article introduces a new holding horizon measure of active management and examines its relation to future risk-adjusted fund performance (alpha). Our measure reveals a wide cross-sectional dispersion in mutual fund investment horizons, and shows that long-horizon funds exhibit positive future long-term alphas by holding stocks with superior long-term fundamentals. Further, stocks largely held by long-horizon funds outperform stocks largely held by short-horizon funds by more than $ 3% $ annually, adjusted for risk, over the following 5-year period. We also find a clientele effect: to reduce liquidity costs, long-horizon funds attract more long-term investors through share classes that carry load fees.