The formation period return difference between past winners and losers, which I call the momentum gap, negatively predicts momentum profits. I document this for the U.S. stock market and find consistent results across 21 major international markets. A one-standard-deviation increase in the momentum gap predicts a 1.25% decrease in the monthly momentum return after controlling for existing predictors. This predictability extends up to 5 years for static momentum portfolios, consistent with time-varying investor biases. Following the simple real-time strategy of investing in momentum only when the momentum gap is below the 80th percentile delivers a Sharpe ratio of 0.78.

Some of the leading theories of momentum have different empirical predictions that depend on market composition and structure. The institutional theory predicts lower momentum profits in markets with less agency. Behavioral theories predict lower profits in markets with more sophisticated investors. In this paper, we use a dataset from a major 19th century equity market to test these predictions. We find no evidence to support the institutional theory due to the lack of delegated management. We exploit a regulatory change in the middle of our sample period to test behavioral theories. We find evidence consistent with overreaction theories of momentum.