Momentum is one of the most empirically robust return anomalies in finance: the tendency for assets that have recently performed well to continue outperforming, and assets that have recently performed poorly to continue underperforming, over intermediate time horizons of 3 to 12 months. Documented across equities, bonds, commodities, currencies, and global markets over more than a century of data, momentum challenges the Efficient Market Hypothesis’s prediction that past returns should have no bearing on future returns.

The Academic Foundation

Jegadeesh and Titman’s seminal 1993 paper showed that U.S. stocks with strong 3-12 month past returns continued to outperform weak past performers over subsequent periods. This finding has been confirmed in virtually every equity market globally, as well as in fixed income, currency, and commodity markets — making momentum one of the most rigorously documented return premiums in the academic literature.

Why Momentum Persists

Despite widespread awareness, momentum has continued to generate returns decades after its documentation. The most compelling explanations are behavioral: investors underreact to new information, causing prices to adjust gradually (driving trend continuation); institutional herding reinforces trends as fund managers follow the same signals; and the slow diffusion of information through investor networks sustains moves past the point where rational updating would have fully priced them in.

Types of Momentum

Cross-sectional momentum ranks a universe of assets by recent performance and allocates to leaders while avoiding laggards — exploiting relative persistence. Time series (absolute) momentum compares each asset’s return to a risk-free rate — holding positively trending assets and exiting negatively trending ones. Both are well-documented; combining them produces more robust results than either alone.

Momentum’s Asymmetric Risks

Momentum strategies carry the asymmetric risk of sudden, violent reversals at major market turning points. Managing this requires active volatility management — reducing position sizes when volatility rises — and absolute momentum filters that exit all positions when broad market trends turn decisively negative, regardless of relative performance rankings.

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