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The momentum factor, the empirical tendency of stocks that have performed well recently to continue performing well in the near future, is one of the most robust and well-documented anomalies in financial markets. Momentum ETFs translate this academic finding into investable strategies, systematically owning the stocks with the strongest recent performance and rebalancing regularly to maintain exposure to market leaders.
For growth investors, momentum ETFs represent a natural complement to fundamental growth analysis. While traditional growth ETFs select stocks based on financial characteristics like revenue growth and earnings expansion, momentum strategies select based on price action, capturing the market’s collective judgment about which companies are winning regardless of the specific fundamental drivers behind their success.
Understanding the Momentum Factor
The momentum premium was first formally documented by Narasimhan Jegadeesh and Sheridan Titman in their landmark 1993 research, which showed that buying recent winners and selling recent losers produced significant excess returns across a wide range of time periods and markets. Subsequent research confirmed that momentum exists in virtually every equity market studied, in bond markets, commodity markets, and currency markets, making it one of the most pervasive factors in finance.
The most common momentum measurement period is 12 months of prior returns, typically excluding the most recent month to avoid short-term reversal effects. Stocks ranking in the top decile of 12-month returns have historically outperformed those in the bottom decile by several percentage points annually. This persistence of trends reflects the behavioral tendency of investors to underreact to positive information, causing prices to adjust to fair value gradually rather than instantaneously.
Several explanations have been proposed for why momentum works. Behavioral finance researchers point to investor biases including anchoring (underreacting to new information), herding (following the crowd), and disposition effect (selling winners too soon and holding losers too long). Risk-based explanations suggest momentum stocks are riskier because they tend to crash violently during market dislocations, and the premium compensates for this crash risk. Both explanations likely contain elements of truth, and the persistence of the momentum premium across decades and markets suggests that its underlying causes are deeply rooted in human psychology and market structure.
Leading Momentum ETFs Compared
Invesco S&P 500 Momentum ETF (SPMO)
SPMO tracks the S&P 500 Momentum Index, which selects the 100 S&P 500 stocks with the strongest 12-month risk-adjusted momentum scores. The fund has seen explosive growth, more than doubling its assets to over $10.5 billion in 2025, reflecting strong investor demand for systematic momentum exposure within the large cap universe.
SPMO’s semi-annual rebalancing schedule reconstitutes the portfolio twice per year, selecting the current highest-momentum stocks and holding them for six months before reassessing. This rebalancing frequency balances the need to capture momentum trends against the trading costs and tax consequences of more frequent reconstitution. The semi-annual approach has contributed to SPMO’s superior risk-adjusted returns compared to more frequently rebalanced peers.
The fund’s concentration in 100 stocks from the S&P 500 provides a high-conviction momentum portfolio while maintaining the liquidity and quality characteristics inherent in the S&P 500 universe. This makes SPMO a relatively conservative approach to momentum investing compared to strategies that include smaller or lower-quality stocks.
iShares MSCI USA Momentum Factor ETF (MTUM)
MTUM is the largest momentum ETF by assets, managing approximately $17 billion. The fund tracks the MSCI USA Momentum SR Variant Index, which selects stocks from the MSCI USA Index based on their risk-adjusted momentum scores calculated from 6-month and 12-month price performance.
MTUM holds approximately 125 stocks and returned 22.15% in 2025, outperforming its category average of 15.54%. The fund earned a Morningstar Silver medal rating, reflecting the research firm’s positive assessment of its process, people, and parent organization.
MTUM’s quarterly rebalancing frequency is higher than SPMO’s semi-annual schedule, which results in more portfolio turnover and potentially higher trading costs. Research suggests that MTUM’s more frequent rebalancing has not translated into improved risk-adjusted returns compared to SPMO, though it may provide quicker adaptation to changing market leadership during periods of rapid rotation.
Other Momentum ETF Options
The iShares MSCI International Momentum Factor ETF (IMTM) applies momentum factor selection to international developed markets, providing non-U.S. momentum exposure that complements domestic momentum ETFs and enhances international portfolio construction.
The JPMorgan U.S. Momentum Factor ETF (JMOM) and the Fidelity Momentum Factor ETF (FDMO) represent additional domestic momentum options with slightly different methodologies and cost structures. Comparing these alternatives helps ensure you’re choosing the momentum implementation that best fits your portfolio needs and cost expectations.
SPMO vs. MTUM: Which Momentum ETF to Choose?
The comparison between SPMO and MTUM is the most common decision point for momentum ETF investors, and the evidence increasingly favors SPMO for most purposes.
SPMO’s semi-annual rebalancing produces lower turnover, lower trading costs, and better tax efficiency compared to MTUM’s quarterly reconstitution. Despite the less frequent rebalancing, SPMO has delivered competitive or superior risk-adjusted returns, suggesting that the momentum factor’s alpha is captured adequately with twice-yearly updates and that more frequent trading adds cost without adding return.
SPMO’s constraint to S&P 500 stocks ensures high liquidity and quality across all holdings, while MTUM’s broader MSCI USA universe can include mid cap stocks that may have lower liquidity. For investors in taxable accounts, SPMO’s lower turnover translates into fewer taxable events and better after-tax returns.
MTUM’s larger asset base and longer track record provide some advantages in terms of fund stability and the depth of historical performance data available for analysis. Its quarterly rebalancing may also be preferred by investors who want faster adaptation to changing market trends, though the evidence suggests this speed comes at a net cost rather than a net benefit.
How Momentum Complements Growth Investing
Momentum and growth are related but distinct investment factors, and combining them provides portfolio benefits that neither achieves alone.
Growth investing selects stocks based on fundamental business characteristics: revenue growth, earnings expansion, market opportunity, and competitive advantage. These fundamental factors drive long-term business value creation and are the foundation of successful growth investing. However, growth factors alone don’t capture timing. A stock can have excellent growth fundamentals but lag in the market for extended periods if investor attention is focused elsewhere.
Momentum adds a timing dimension to the portfolio by ensuring exposure to the stocks that are currently being recognized and rewarded by the market. When a growth stock’s strong fundamentals begin translating into stock price appreciation, momentum signals capture this transition, and momentum ETFs systematically add these accelerating winners to their portfolios.
The overlap between momentum and growth varies significantly over time. During growth-led markets, momentum portfolios naturally tilt heavily toward growth stocks, creating high correlation. During value rotations, momentum portfolios shift toward value and cyclical stocks, creating differentiation from growth holdings. This adaptive nature means momentum ETFs provide a form of systematic market regime adaptation that static growth allocations lack.
Combining a core growth ETF like VUG with a momentum ETF like SPMO creates a portfolio that benefits from both fundamental growth characteristics and price trend confirmation. Positions that appear in both your growth and momentum allocations have particularly strong signals, as they combine business quality with market recognition.
Momentum Risks and Drawdowns
Despite its strong long-term performance record, the momentum factor experiences characteristic drawdowns that investors must understand and prepare for.
Momentum crashes occur when the prevailing market trend reverses sharply, causing recent winners to plunge and recent losers to surge. These crashes tend to happen at market turning points, particularly during recoveries from bear markets when the stocks that declined most during the downturn rally most aggressively, punishing the momentum strategy that had been positioned in the previous winners.
The most severe momentum drawdowns have historically been concentrated in short, violent periods rather than prolonged declines. A momentum ETF might underperform its benchmark by 10% to 20% in just a few weeks during a sharp market rotation, only to recover as a new trend establishes itself. This drawdown pattern requires investors to maintain their positions through the pain rather than panic-selling at the worst possible time.
Crowding risk has increased as momentum ETFs have grown in assets. When many investors follow the same momentum signals and hold the same momentum stocks, the concentrated positions can become vulnerable to rapid unwinding if sentiment shifts. The more assets flowing into momentum strategies, the more pronounced the buying pressure on current winners and the more violent the eventual correction when those stocks lose momentum.
Portfolio Integration Strategies
Incorporating momentum ETFs into a growth portfolio requires thoughtful allocation sizing and combination with other portfolio elements.
A moderate momentum allocation of 10% to 20% of the equity portfolio provides meaningful factor exposure without dominating the portfolio’s characteristics. This allocation level allows momentum to contribute to returns during trending markets while limiting the damage during momentum crashes.
Combining momentum with quality and low volatility factor exposures can create a multi-factor portfolio that is more robust across different market environments than any single factor alone. The quality factor provides downside protection during market stress, while low volatility reduces the portfolio’s sensitivity to market sell-offs. Together with momentum, these factors create a portfolio with higher risk-adjusted returns and smoother performance than the broad market.
Rebalancing momentum positions requires balancing two competing forces. Allowing momentum positions to run captures the trend-following benefit of the strategy, but letting them grow unchecked creates concentration risk. Periodic rebalancing back to target allocations manages this trade-off, though the optimal rebalancing frequency for momentum positions may be less frequent than for other portfolio components given the strategy’s inherent trend-following nature.
Monitor the factor exposure of your momentum ETF relative to your other growth holdings. During periods when momentum and growth factors are highly correlated, your effective growth exposure may be larger than intended, requiring adjustment. During periods when momentum diverges from growth, the combination provides genuine diversification that improves risk-adjusted returns.
Conclusion: Momentum as a Systematic Growth Enhancer
Momentum ETFs offer growth investors a disciplined, systematic approach to capturing one of the most well-documented return anomalies in financial markets. By owning the stocks with the strongest recent performance and rebalancing regularly, momentum strategies provide a form of automated trend following that can enhance returns during trending markets while complementing fundamental growth analysis with market-driven signals.
SPMO and MTUM represent the two leading momentum ETF options, with SPMO offering advantages in cost efficiency, rebalancing approach, and risk-adjusted returns that make it the preferred choice for most investors. Combined with core growth ETF holdings and other factor exposures, a moderate momentum allocation can improve portfolio diversification and long-term returns.
The key to successful momentum investing is understanding and accepting the strategy’s characteristic risk profile, including the possibility of sharp short-term drawdowns during market rotations. Investors who maintain their momentum allocations through these challenging periods and avoid the temptation to sell after drawdowns are rewarded over the long term with one of the market’s most persistent sources of excess return. As with all growth strategies, patience and discipline ultimately determine whether the momentum premium translates into real wealth creation in your portfolio.
