Momentum investing: one of the most documented effects in finance
Momentum investing is among the most extensively replicated findings in financial research. The principle is straightforward: assets that have performed well over the recent past tend to continue outperforming, and those that have underperformed tend to continue lagging.
The difficulty is not demonstrating the effect. It is holding a momentum position through the periods when the effect reverses. This happens often violently, often at the worst possible moment, and always in a way that tests whether the investor really understands what they own.
What momentum investing actually is
Cross-sectional momentum ranks assets relative to each other: the strategy goes long recent winners and short recent losers within a defined universe, typically measured over 3 to 12 months with the most recent month skipped to avoid contamination from short-term reversal. The position is not a view on where markets are going. It is a view on which assets are likely to continue leading or lagging their peers. The portfolio is rebalanced regularly as the ranking changes, meaning the strategy is always long whatever has been working and short whatever has not.
Time-series momentum (the foundation of most trend-following strategies) is a related but distinct concept. Rather than ranking assets against each other, it looks at each asset relative to its own history and takes a long or short position based on each asset’s own recent trajectory. Cross-sectional momentum in equities and time-series momentum in futures markets share a common academic pedigree but have different risk profiles, different implementation requirements, and different crash dynamics. They should not be evaluated as if they are the same strategy with a different name.
The crash problem
Momentum strategies have a specific and well-documented vulnerability. They tend to accumulate large short positions in beaten-down assets: assets that have been underperforming, often for fundamental reasons, and that have the profile of deeply discounted, high-leverage, optionlike payoffs. In normal conditions, these positions continue to drift lower. At a market inflection point those exact positions absorb the most violent positive return shock.
The mechanism is not random. It is structural. A momentum portfolio positioned for continuation is almost by definition positioned against a sharp reversal. When the market recovers strongly from a distressed level, the short side of the momentum book surges. The long side lags or declines. The strategy can produce severe losses at precisely the moment a conventional equity investor is experiencing recovery. For an investor who does not understand this dynamic in advance, the experience is deeply disorienting and difficult to hold through.
- The equity market bottomed in early March 2009. The momentum portfolio’s long book (defensives and recent outperformers) was positioned for conditions that no longer applied. The short book(financials, cyclicals, the worst performers of 2008) was positioned against assets about to experience a violent recovery bounce
- Equity momentum strategies saw drawdowns of 60% or more in the March–May window, against a market that was recovering sharply. The strategy did not merely underperform, it moved in the structurally opposite direction to what most investors expected from a diversifying factor
- The mechanism had been characterised in advance: Daniel and Moskowitz identified that momentum crashes are predictable in character if not in timing, occurring at market inflection points following prolonged bear markets when optionlike short positions absorb the recovery premium
- The lesson is not that momentum is broken; it recovered and remains documented in subsequent periods. The lesson is that investors who cannot hold through a 60% drawdown in a factor position should not hold momentum, regardless of what the long-run Sharpe ratio says in a presentation deck
What allocators need to evaluate
“The research on momentum is among the clearest in finance. The part that receives less attention is the return distribution, specifically the crash episodes that look structurally like the factor is broken, right before it recovers.”
Three evaluation dimensions are specific to momentum strategies. First: cross-sectional or time-series, and in which asset classes? The risk profile differs meaningfully. Cross-sectional equity momentum is most exposed to the crash dynamic described above. Time-series momentum in futures markets has a different reversal profile and tends to sit inside trend-following frameworks with their own crash characteristics. Second: what is the rebalancing frequency, and what transaction costs does the strategy actually incur? Higher frequency means faster response to a reversal but also higher cost drag. Third: what is the investor’s genuine drawdown tolerance? Not the stated tolerance in a subscription document but the real emotional and institutional tolerance for a −50% period in a factor position that the rest of the portfolio is not sharing.
Modifications matter too. Momentum combined with volatility scaling, downside hedging, or regime filters behaves differently from raw factor exposure. Managers should be specific about which version they are running and why, and the modifications should appear in the live track record, not only in the backtest.
Momentum investing questions investors ask
Related but distinct. Cross-sectional momentum ranks assets against each other within a universe and rotates exposure toward recent winners. Trend following (time-series momentum) looks at each asset relative to its own history and takes long or short positions based on each asset’s own trajectory. Trend following is more commonly associated with CTAs and diversified futures portfolios; cross-sectional momentum is more common in equity factor investing. The crash dynamics differ: cross-sectional momentum is particularly vulnerable at equity market inflection points; trend following tends to struggle in sharp reversals across multiple asset classes simultaneously.
The academic foundation is Jegadeesh and Titman’s 1993 paper on U.S. equities. Since then, momentum has been documented across international equity markets, fixed income, currencies, and commodities, and across historical time periods extending more than 100 years. It is among the most replicated findings in empirical finance. That breadth of evidence is meaningful but it does not make any particular implementation robust. It also does not eliminate the crash risk that is inherent in how the factor is constructed.
A momentum crash is a period when the strategy reverses violently, typically coinciding with a sharp market recovery following a prolonged bear market. They are infrequent but not rare. The most severe documented instance was March to May 2009. Historical analysis extending back to the 1920s finds several severe episodes, with drawdowns concentrated in a matter of weeks and often exceeding 40%. The distinguishing feature is not the drawdown depth alone; it is the timing, which tends to arrive when a conventional equity investor’s portfolio is beginning to recover.
Momentum investing: 100 years of evidence, and one question most investors get wrong before they allocate
The academic evidence on momentum is not in dispute. What is consistently underestimated is the tail of the distribution. More specifically, it’s the investor’s ability to hold through a −60% drawdown in a factor position while everything else in their portfolio is recovering. The investors who succeed with momentum exposure are usually the ones who understood that scenario before they entered, not after.
If you are evaluating a momentum-based strategy and want a second perspective on the implementation and the distribution before you allocate, reach out.
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