Quantitative Momentum: A Practitioner's Guide to Building a Momentum-Based Stock Selection System
Summary
Wesley Gray and Jack Vogel run Alpha Architect and wrote this as a companion to their earlier Quantitative Value, applying the same method: survey the academic evidence for a factor, then build an explicit portfolio construction process from it.
The evidence section covers the momentum literature, principally Jegadeesh and Titman's finding that stocks with high returns over the prior three to twelve months continue to outperform over the following months. Gray and Vogel argue that momentum persists because of behavioural causes, specifically underreaction to information and delayed overreaction, and that it survives because arbitrage is limited by career risk: momentum strategies produce long periods of underperformance that professional managers cannot survive.
Their construction rules are specific. Use intermediate-term momentum, measured over twelve months excluding the most recent month, because the recent month exhibits short-term reversal. Prefer stocks whose price path has been smooth, which they call the frog in the pan hypothesis, on the argument that gradual moves attract less attention and therefore produce more continued drift than jumpy ones. Concentrate the portfolio rather than diversifying, since diluting the signal dilutes the return. Rebalance frequently, quarterly rather than annually, because momentum decays. Attend to seasonality, since momentum performance varies systematically across the calendar. The backtests are their own and readers should discount accordingly; momentum strategies are also tax-inefficient and turnover-heavy, which the book acknowledges but does not fully cost.
Key takeaways 7
- Momentum measured over twelve months excluding the most recent month outperforms measures that include the recent month, because of short-term reversal.
- Stocks whose price path has been smooth show stronger continuation than those that moved in jumps.
- Concentrating a momentum portfolio into the strongest signals produces higher returns than diversifying across many names.
- Momentum decays quickly, which requires quarterly or more frequent rebalancing and produces high turnover.
- Momentum persists because it produces long stretches of underperformance that professional managers cannot survive holding.
- Momentum and value factors are negatively correlated, which makes combining them more effective than either alone.
- The strategy is tax-inefficient and expensive to trade, so its net return to a taxable investor is far below the backtested gross figure.
Who should read it
Investors implementing systematic equity strategies who want explicit construction rules for a momentum portfolio and the evidence behind each choice.
About Wesley R. Gray
Founder and CEO, Alpha Architect; formerly assistant professor of finance at Drexel University's LeBow College of Business; former U.S. Marine Corps captain
Quantitative Value and Quantitative Momentum are the standard build-it-yourself manuals for systematic value and momentum, and Alpha Architect is a heavily used practitioner research archive.
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Topics