Momentum Factor Investing: Riding the Trend
Momentum — buying stocks with strong 6-12 month returns — has generated over 3% annualized excess returns since 1927. The momentum premium works across asset classes: stocks, bonds, currencies, and commodities. But momentum can crash suddenly during market reversals.
Momentum factor investing is the strategy of buying securities that have performed well over the past 6-12 months and selling those that have performed poorly. First documented by Jegadeesh and Titman (1993), the momentum premium is one of the most pervasive anomalies in finance. It works not only across US stocks but also in international equities, bonds, currencies, and commodities. The typical momentum strategy ranks stocks by their total return over the past 12 months (skipping the most recent month to avoid short-term reversals), buys the top decile, sells the bottom decile, and rebalances monthly.
The source of momentum is debated between behavioral and risk-based explanations. The behavioral view argues that investors underreact to new information (anchoring bias) and then overreact when the trend becomes obvious (herding behavior). Investors are slow to update their beliefs about earnings trends, causing prices to adjust gradually. Once the trend is established, investors pile on, creating a self-reinforcing cycle. The risk-based explanation suggests that momentum stocks have higher exposure to certain risk factors that command a premium. Regardless of the source, momentum's historical performance is compelling: a long-short momentum portfolio generated over 10% annualized returns from 1927-2020 in US data.
Real-world example: An investor who allocated $10,000 to MTUM (iShares MSCI USA Momentum Factor) at inception (2013) and $10,000 to SPY would have seen MTUM significantly outperform during strong bull markets. From 2013-2021, MTUM returned approximately 16% annualized vs 14% for SPY, turning $10k into $36,000 vs $29,000. However, momentum crashed in 2022 (down 25%) as the market rotated from growth to value, and in March 2020 COVID crash, momentum experienced a sharp reversal. The momentum strategy also suffered in 2009 (-39% for momentum factor) when the market bottomed and the previous winners (banks, financials) were the hardest hit. These momentum crashes are the strategy's primary risk. Quality factor investing →
Implementing Momentum Factor Investing with ETFs
The most popular momentum ETF is MTUM (iShares MSCI USA Momentum Factor, 0.15% ER), which holds the top 30% of US stocks ranked by 6-month and 12-month price momentum. It rebalances semi-annually. For international momentum, IMOM (iShares MSCI Intl Momentum Factor, 0.20% ER) covers developed markets outside the US. For a multi-asset momentum approach, AQMIX (AQR Multi-Style Fund) incorporates momentum across stocks, bonds, and currencies. For do-it-yourself implementation, screen stocks using the Portfolio123 or Finviz platform. A simple momentum portfolio could be 10-15% of equity in MTUM and 5-10% in IMOM. Pair momentum with value to smooth performance — value and momentum have historically been negatively correlated, with momentum excelling in strong trends and value excelling in reversals. A 50/50 value/momentum combination has significantly higher risk-adjusted returns than either factor alone.
FAQs
Why skip the most recent month when calculating momentum?
Academic research (Jegadeesh, 1990) shows that stocks experience short-term reversal in the very near term (1 month). Stocks that went up last week tend to go down this week. By skipping the most recent month when calculating momentum, the strategy avoids this short-term reversal effect and captures the medium-term continuation. This is standard practice in momentum research. The typical momentum signal uses months t-12 to t-1 (skipping the most recent month) to rank stocks. ETFs like MTUM incorporate this skip-month approach in their methodology.
How do I protect my momentum portfolio from crashes?
Momentum crashes are sudden and severe, typically occurring during market reversals when the trend breaks sharply. Protection strategies include: combining momentum with value (50/50 allocation smoothes performance dramatically), using trailing stop losses on momentum positions, incorporating volatility scaling (reduce position size when volatility is high), and diversifying across asset classes (momentum in bonds and currencies reduces equity momentum crash risk). The simplest approach is to pair momentum with value (AVUV + MTUM) — these two factors have the strongest negative correlation among all factor pairs. A 50/50 AVUV/MTUM portfolio has significantly higher Sharpe ratio than either alone.
Is momentum factor investing tax-efficient?
Momentum is one of the least tax-efficient factors. The strategy requires frequent rebalancing (monthly or semi-annually) as stocks move in and out of momentum ranks. This turnover generates short-term capital gains, which are taxed as ordinary income. MTUM rebalances semi-annually, which reduces turnover but still generates more taxable gains than a buy-and-hold strategy. For this reason, momentum ETFs are best held in tax-advantaged accounts (IRA, 401k). In taxable accounts, consider pairing momentum with tax-loss harvesting or using a tax-managed momentum strategy. Some newer ETFs like QVAL (Alpha Architect Value Momentum) combine value and momentum in a single fund to reduce turnover and improve tax efficiency.