The Momentum Factor: Evidence, Construction and Crashes

Momentum Factor

The momentum factor buys recent winners and sells recent losers. Learn how it is built, the evidence across markets, momentum crashes and how to manage them.

Advanced3 min readUpdated 3 Oct 2026

Lesson 30 of 38

The momentum factor captures the tendency of assets that have performed well over the past several months to keep outperforming, and of poor performers to keep underperforming. Momentum is one of the most robust patterns in finance, found in stocks, bonds, currencies and commodities across many countries and over two centuries of data. It also has a dark side: rare but severe crashes. This lesson covers momentum as a systematic factor; the trading style is covered in Momentum Trading.

Two kinds of momentum#

Type	Compares	Lesson
Cross sectional momentum	Each asset against others: buy relative winners, sell relative losers	This lesson
Time series momentum	Each asset against its own past: long if it has risen, short if it has fallen	Trend Following

Building a momentum factor#

The standard academic construction (often called UMD, "up minus down", or WML, "winners minus losers"):

Measure each stock's return over the past 12 months, skipping the most recent month (to avoid short term reversal). See Short and Long-Term Reversal.
Rank stocks by this return.
Buy the top group (for example, the top 30%) and short the bottom group.
Rebalance monthly.

The evidence#

Jegadeesh and Titman (1993) found that buying past 3 to 12 month winners and selling losers earned about 1% a month in US stocks from 1965 to 1989.
Rouwenhorst (1998) found momentum in 12 European markets.
Asness, Moskowitz and Pedersen (2013) documented momentum across asset classes.
Geczy and Samonov (2016) found momentum in US stock data going back to 1801.

Why might momentum work?#

Explanation	Idea
Underreaction	Investors adjust slowly to new information, so prices drift. See Earnings Reactions and Post-Earnings Drift
Herding and feedback	Rising prices attract more buyers
Disposition effect	Investors sell winners too early and hold losers, slowing price adjustment. See Disposition Effect
Risk	Momentum may compensate for crash risk

Momentum crashes#

Managing momentum risk#

Technique	How it helps
Volatility scaling	Reduce exposure when momentum volatility is high; research by Barroso and Santa Clara (2015) found this greatly reduced crashes
Combine with value	Value and momentum are negatively correlated. See Combining Signals
Industry neutral momentum	Removes large sector bets
Avoid concentrated shorts in distressed stocks	Reduces squeeze risk
Residual momentum	Uses returns after removing factor exposures

Costs and turnover#

Momentum has high turnover, often 200% to 400% a year for monthly rebalanced portfolios, so trading costs take a meaningful share of returns, especially in small caps. Buffers and slower rebalancing help. See Signal Turnover, Breadth and Neutralization.

Frequently asked questions#

What is the momentum factor?#

A systematic strategy that buys assets with strong recent performance, typically over 12 months excluding the last month, and sells those with weak performance.

Why skip the most recent month in momentum?#

Because returns over the most recent month tend to reverse in the short term, which would weaken the momentum signal.

What causes momentum crashes?#

Sharp market rebounds after declines, when beaten down past losers rally much more than past winners, as in 2009.

Next, learn about profitable, stable companies in Quality and Profitability Factors.

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Next lessonQuality and Profitability FactorsThe quality factor favours profitable, stable, conservatively financed companies. Learn how quality is measured, the evidence and how it pairs with value.