Factor Investing
Factor investing is an investment approach that targets specific, well-documented characteristics (factors) that have historically been associated with higher risk-adjusted returns across asset classes.
Factor investing emerged from decades of academic research showing that much of the variation in stock returns can be explained by a relatively small number of persistent characteristics rather than by manager skill alone. The most foundational factor work was done by Eugene Fama and Kenneth French, whose three-factor model (1993) extended CAPM by adding size (small-cap stocks tend to outperform large-cap stocks) and value (cheap stocks by book-to-price tend to outperform expensive ones) as additional explanatory variables.
Subsequent research identified additional robust factors including momentum (recent winners tend to keep winning), profitability (highly profitable firms outperform low-profit firms), investment (firms that invest conservatively outperform those that invest aggressively), and low volatility (stocks with lower historical volatility have generated surprisingly competitive returns on a risk-adjusted basis). These factors collectively form the foundation of what is now called the multi-factor or smart beta universe.
The commercial appeal of factor investing is that it makes systematic risk premia accessible at low cost through rules-based ETFs and index funds, rather than paying active manager fees for exposure that can be replicated mechanically. A value factor ETF, for example, will regularly screen and rebalance into the cheapest quintile of stocks by price-to-book, delivering systematic value exposure without the need for a highly paid stock-picker.
Factors are most credible when they have: a long historical track record spanning multiple decades and market cycles; economic intuition for why the premium should exist (whether risk-based or behavioral); pervasiveness across different markets and asset classes; and robustness to different definitions and implementation choices. The value, momentum, size, profitability, and low-volatility factors broadly meet these criteria.
A key challenge is factor cyclicality. Individual factors can underperform for extended periods. The value factor, for instance, severely underperformed growth from roughly 2007 through 2020, testing the conviction of many factor investors. Multi-factor portfolios that combine factors with low correlations to each other can reduce the severity of these dry spells while still capturing the long-run premia that each factor individually offers.