The Three Biggest Myths about Factor Investing

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This article originally appeared on ETF.COM here.

As the chief research officer for Buckingham Strategic Wealth and the BAM Alliance, I receive many questions from advisors and investors regarding concerns about factor-based investment strategies. A brief background on factor-based investing is helpful before discussing those concerns.

William Sharpe, Jack Treynor, John Lintner and Jan Mossin are typically given most of the credit for introducing the first formal asset pricing model – the capital asset pricing model (CAPM). It was important because it provided the first precise definition of risk and how it drives expected returns.

The CAPM looks at returns through a “one actor” lens, meaning the risk and return of a portfolio is determined only by its exposure to market beta. In the 1993 publication of the study “Common Risk Factors in the Returns on Stocks and Bonds,” Eugene Fama and Kenneth French proposed a new asset pricing model, which became known as the “Fama-French three-factor model.” This model proposes that, in addition to the market beta factor, exposure to the factors of size and value further explain the cross section of expected stock returns.

The authors demonstrated that we live not in a one-factor world but in a three-factor world. They showed how the risk and expected return of a portfolio is explained by not only its exposure to market beta but by its exposure to the size (small stocks) and price (stocks with low prices relative to book value, or value stocks) factors.

Fama and French hypothesized that, while small-cap and value stocks have higher market betas (more equity-type risk), they also contain additional unique risks (they are not free lunches) unrelated to market beta. The Fama-French three-factor model improved the explanatory power from about two-thirds of the differences in returns between diversified portfolios to more than 90%.

The Fama-French model became the workhorse model for financial economists. The fund family Dimensional Fund Advisors (Fama and French led their research efforts) led the way in introducing factor-based funds based on the Fama-French research. (Full disclosure: My firm, Buckingham Strategic Wealth, recommends Dimensional funds in constructing client portfolios.)