One Brief Shining Moment(um) - Past Momentum Performance and Momentum Reversals

Motivated by behavioral theories, we test whether recent past performance of the momentum strategy (Past Momentum Performance—PMP) negatively predicts the per-formance of stale momentum portfolios. Following periods of top-quintile PMP, mo-mentum portfolios exhibit strong reversals 2-5 years after formation, whereas, following periods of bottom-quintile PMP, stale momentum portfolios earn positive returns. The difference in cumulative five-year Fama-French alphas for momentum portfolios formed in high- and low-PMP months is 40%. A value-weighted trading strategy based on this effect generates an alpha of 0.40% per month (t = 3.74). These patterns are confirmed in international data. These findings present a puzzle for existing theories of momentum.