Momentum investing

Momentum investing is a strategy rooted in the observation that stocks that have outperformed recently tend to continue outperforming for a time, and those that have underperformed tend to lag further. The strategy buys winners and sells (or avoids) losers.

The momentum premise

Momentum rests on a simple observation: markets exhibit trends. When a stock starts moving up, it often continues for a while. When it starts down, sellers often pursue it further. This is not a claim that price trends contain information about the future — momentum can persist through noise, herding, and sentiment shifts.

The psychological explanation is varied: investors discover good news and pile in; bad news creates panic; fund flows and rebalancing create mechanical buying and selling pressure; behavioral biases like anchoring and representativeness bias cause trends to persist.

Screening for momentum

Momentum investors typically hunt for:

• 6–12-month relative strength. The stock’s return over the past six to twelve months, compared to the market or a benchmark. Top-ranked stocks are bought; bottom-ranked are avoided or sold short.
• Accelerating earnings or revenue. Earnings surprises and accelerating growth feed momentum.
• Positive stock market breadth. When the broad market is rallying, more stocks exhibit positive momentum. When breadth is deteriorating, momentum becomes fragile.
• Institutional buying. Unusual option activity, increased short interest, or insider buying can signal momentum onset.
• Sector momentum. If the sector is rallying, individual momentum picks within that sector perform better.

The reversal hazard

Momentum is a self-limiting strategy. Trends do not persist indefinitely. A stock that has tripled on momentum is eventually hit by: profit-taking, valuation exhaustion, earnings disappointment, or mean reversion. A momentum investor must sell or trim before the reversal, which requires discipline.

This is where timing becomes critical and luck plays a large role. Exiting too early forfeits further gains; exiting too late catches the downturn.

Momentum versus mean reversion

The relationship is temporal. Over days and weeks, momentum dominates — trends persist. Over months and years, mean reversion dominates — prices revert toward intrinsic value. The best-disciplined momentum investors have explicit exit rules based on time and price targets, not vague “ride the winners” intuition.

See also