We propose a rational theory of momentum and reversal based on delegated portfolio management. A competitive investor can invest through an index fund or an active fund run by a manager with unknown ability. Following a negative cashflow shock to assets held by the active fund, the investor...

We propose a rational theory of momentum and reversal based on delegated portfolio management. Flows between investment funds are triggered by changes in fund managers' efficiency, which investors either observe directly or infer from past performance. Momentum arises if fund flows exhibit...