Momentum Factor Investing with ETFs
Momentum is the factor that feels most like chasing — and it has one of the strongest academic records. Here's how it works, why it pays, and how it can crash.
Don't have time? Here's what you need to know:
- 1Momentum buys stocks with strong 6–12 month trailing returns and is backed by Jegadeesh and Titman (1993) and decades of follow-up evidence.
- 2MTUM, the largest U.S. momentum ETF, rebalances semiannually and charges about 0.15% — higher than an index fund because the strategy trades frequently.
- 3Momentum has historically been lowly correlated with value, making the two a natural pair in multi-factor portfolios.
- 4Its main risk is the momentum crash: sharp losses when market leadership reverses, as in the 2009 recovery.
The One Factor That Says 'Buy What's Winning'
Momentum is the tendency for stocks that have performed well over the past 6 to 12 months to keep outperforming over the next several months, and for recent losers to keep lagging. It is the one major factor that explicitly rewards chasing recent strength — which makes it feel uncomfortable to disciplined investors trained to buy low and sell high.
Yet momentum has one of the most robust track records in all of academic finance. Documented by Jegadeesh and Titman in 1993 and confirmed across decades, countries, and even asset classes, the momentum effect is hard to dismiss. A momentum ETF ranks stocks by their recent trailing returns (usually excluding the most recent month) and holds the strongest, rebalancing periodically as leadership rotates.
How a Momentum ETF Like MTUM Works
The largest U.S. momentum fund is MTUM, which tracks an MSCI momentum index of large- and mid-cap U.S. stocks. It scores each stock on its risk-adjusted price performance over roughly the past 6 and 12 months, selects the highest scorers, and rebalances semiannually — or sooner if markets move violently. The expense ratio is around 0.15%, higher than a plain index fund because the strategy trades more.
That turnover is the defining feature of momentum. Because leadership rotates, a momentum fund must continually sell fading winners and buy new ones, which generates trading costs and, in a taxable account, more taxable events than a buy-and-hold index fund. The portfolio also looks very different from the market at any moment — heavily concentrated in whatever sector has been leading, which can be technology one year and energy the next.
| Feature | MTUM (momentum) | Plain S&P 500 index fund |
|---|---|---|
| What it holds | Recent 6-12 month winners | The whole large-cap market by size |
| Rebalancing | Semiannual (or sooner in stress) | Only as the index reconstitutes |
| Expense ratio | ~0.15% | ~0.03% |
| Turnover / tax efficiency | High — best held in a tax-advantaged account | Low — very tax-efficient |
Tip: Momentum's high turnover makes it more tax-efficient inside an IRA or 401(k) than in a taxable brokerage account. Consider where you hold it.
Why Momentum Has Historically Paid
The leading explanation is behavioral. Investors underreact to good news at first — prices drift up gradually as the market digests it — and then overreact, pushing winners past fair value before the trend breaks. Momentum tries to capture the middle of that move. A risk-based explanation also exists: momentum stocks may be exposed to risks that show up sharply in crashes.
Crucially, momentum has historically been lowly or negatively correlated with value. When cheap stocks lag, recent winners often lead, and vice versa. That diversification is why momentum and value are frequently paired in multi-factor strategies — the two factors tend to take turns, smoothing the combined ride.
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The Risk: Momentum Crashes
Momentum's Achilles' heel is the sharp reversal. Because the strategy piles into whatever has been winning, it is heavily exposed at exactly the moments leadership snaps — typically when a falling market suddenly rebounds. In violent market turns, beaten-down stocks rocket and the prior winners momentum holds get left behind, producing brief but severe 'momentum crashes.' Researchers including Kent Daniel have documented these episodes, notably in the 2009 recovery.
The other risk is the obvious one: momentum can simply stop working for stretches, and its higher fees and turnover are a constant drag it must overcome. As with every factor, the premium is not guaranteed. Momentum is best understood as a high-turnover, sometimes-volatile tilt that diversifies a value-heavy portfolio — not as a reliable shortcut to beating the market.
Important: Momentum is most fragile right after a market crash, when leadership can reverse overnight. Do not judge the strategy by its behavior in a single sharp recovery.
Frequently Asked Questions
Isn't momentum just performance chasing?
Mechanically, yes — but it is systematic and rules-based, not a hunch. A momentum ETF ranks stocks by recent trailing returns and rebalances on a schedule. The academic evidence (Jegadeesh and Titman, 1993, and many follow-ups) shows this disciplined version of 'buy the winners' has historically earned a premium, unlike the impulsive chasing individual investors do.
Why is MTUM more expensive than a plain index fund?
Because momentum requires regular trading. Leadership rotates, so the fund must sell fading stocks and buy new winners, typically rebalancing twice a year or more. That turnover drives MTUM's roughly 0.15% expense ratio, versus around 0.03% for a market-cap index fund, and also makes it less tax-efficient in a taxable account.
What is a momentum crash?
A sharp, short-lived loss that hits momentum strategies when market leadership suddenly reverses — usually when a falling market rebounds and beaten-down losers surge while recent winners lag. The 2009 recovery is the textbook example. These crashes are rare but severe, and they are the main risk of holding momentum.
Should I pair momentum with value?
It is a common approach because the two factors have historically been lowly correlated — value tends to lead when momentum lags. Holding both, or a multi-factor fund that blends them, can smooth returns. The cost is that combining factors dilutes the potential payoff of whichever one is working at the time.
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Alex Harrington
CFA Level II Candidate, Finance & Economics
Alex Harrington is an independent ETF researcher and personal finance writer with over 8 years of experience analyzing exchange-traded funds. A CFA Level II candidate with a background in economics, Alex has reviewed 800+ ETFs and helped thousands of beginners build their first investment portfolios through clear, jargon-free education.
This content is for educational purposes only and does not constitute financial advice. Past performance does not guarantee future results. Consult a licensed financial advisor before making investment decisions.