The Momentum Factor
Winners keep winning — the most robust anomaly in finance, and its crash risk.
The momentum factorBuying recent winners and avoiding recent losers. systematically buys recent winners and avoids (or shorts) recent losers — typically ranking stocks by their trailing 6–12 month returns. It’s often called the most robust anomaly in all of finance.
MomentumBuying recent winners and avoiding recent losers. is extraordinary because it *persists across nearly every market and asset classA group of investments with similar behaviour. ever studied, and it’s the factor that most directly contradicts the “buy low” instinct — you’re deliberately buying what’s already gone up. It works for behavioural reasons (Module 1): investors under-react to news at first (so winners keep drifting up as the crowd slowly catches on), then over-react (herding extends the move). Its persistence is partly because* buying expensive-looking winners feels so wrong that most people can’t do it. But momentumBuying recent winners and avoiding recent losers. has a dark side: a momentum crash. Because it piles into crowded winners, momentum can suffer sudden, violent reversals — especially at sharp market turns (e.g. a vicious bear-market rebound), when yesterday’s losers rocket and yesterday’s winners collapse. So momentum offers the most reliable long-run edgeA repeatable, structural reason your trades win over time. and the scariest tail riskThe risk of rare, extreme events (black swans).; it pairs beautifully with value (which zigs when momentum zags) precisely because their crash conditions differ.
- What it is — buy recent winners (top trailing 6–12m returns), avoid recent losers; rebalanced regularly.
- Why robust — documented across countries, asset classesA group of investments with similar behaviour. and centuries; rooted in under- then over-reaction.
- Why it persists — buying expensive-looking winners feels wrong, so most can’t exploit it.
- The dark side — momentumBuying recent winners and avoiding recent losers. crashes: sudden violent reversals at sharp market turns (losers rocket, winners collapse).
ExampleAfter a deep bear marketSustained rising (bull) or falling (bear) market phases., the sharpest early rebound often lifts the most beaten-down (lowest-momentumBuying recent winners and avoiding recent losers.) stocks fastest, while the prior “safe winners” lag — a textbook momentumBuying recent winners and avoiding recent losers. crash that can inflict a brutal short-term loss on a pure momentum portfolio, even though the long-run edgeA repeatable, structural reason your trades win over time. remains strong. This is why momentum is usually combined with steadier factorsTilting a portfolio toward traits that have historically paid..
Key takeawayThe momentum factorBuying recent winners and avoiding recent losers. buys recent winners and avoids losers — the most robust anomaly in finance (persistent across markets and eras, rooted in under/over-reaction), persisting because buying winners feels wrong. Its tail riskThe risk of rare, extreme events (black swans). is the *momentumBuying recent winners and avoiding recent losers. crash*: violent reversals at sharp turns — which is why it pairs well with value.
FAQs
Isn’t buying stocks that already rose just chasing?
Disciplined, systematic momentum differs from emotional chasing: it ranks objectively, rebalances on rules, diversifies across many names, and rests on decades of evidence. The danger isn’t momentum itself but doing it *without rules* or *over-concentrated* — and ignoring its crash risk. Done systematically and combined with other factors, it’s a well-documented edge, not mere chasing.