Factor InvestingCopy Anchor Link

Factor InvestingCopy Anchor Link

Factor investing is the systematic attempt to earn the return premia attached to measurable stock characteristics — size, value, momentum, quality — rather than to any single security's story. Its origin is the collapse of the single-factor view that a stock's expected return is set by its market beta alone.

The curriculum traces the history precisely. A return-generating model expresses expected excess return as the sum of factor exposures times factor premia; the simplest is the single-index model, with the market as the only factor. That model proved inadequate, and the multi-factor extension is credited to two names: Eugene Fama and Kenneth French suggested that a return-generating model for stock returns should include relative market capitalization of the company (size) relative book-to-market value of the company in addition to beta, and "Mark Carhart (1997) extended the Fama and French model by adding another factor: momentum, defined as relative past stock returns." The curriculum further distinguishes the types of multi-factor models — macroeconomic, fundamental, and statistical — while warning that statistical factors "may generate many spurious factors that are devoid of any economic meaning."

The same premia show up, independently, in Tweedy, Browne's compilation What Has Worked in Investing — the empirical case that Graham-style criteria keep working. Its catalog of characteristics associated with exceptional long-term returns reads like a factor list: low price relative to book value, low price relative to earnings, low price relative to cash flow, high dividend yield, small market capitalization, a significant decline in price, and insider accumulation. The studies it assembles quantify each: over 1966–1984 the lowest price-to-book decile returned 14.36% compounded annually against 6.06% for the highest; and Fama and French's own 1992 work found that price-to-book value "is consistently the most powerful for explaining the cross-section of average stock returns."

The crucial interpretive question — and the bridge to value investing — is why the premia persist. Lakonishok, Shleifer, and Vishny conclude that "value strategies yield higher returns because these strategies exploit the mistakes of the typical investor and not because these strategies are fundamentally riskier"; their downside analysis showed the value strategy "does not expose investors to greater downside risk." This is the fork between two readings of the same data. The efficient-markets reading treats the premia as compensation for risk; the behavioral reading, favored in the corpus, treats them as the reward for buying what the crowd has over-discounted — which is mr-market territory and the statistical form of margin-of-safety.

The overlap with value investing is real but not identity. A value investor buys a specific underpriced business after fundamental analysis; a factor investor buys a diversified basket of stocks that score on a cheapness characteristic. The factor approach systematizes exactly what the value investor does by judgment, and the two part company where factor screens buy statistical cheapness that a value investor would reject as low quality. Tweedy, Browne themselves describe the characteristics as clues that "pointed, like clues, in the direction of truly undervalued companies" — a screen, not a verdict.

Momentum is the outlier. It is not a cheapness characteristic — it is the tendency of recent winners to keep winning — and it sits in tension with the contrarian, buy-the-decline instinct of the rest of the corpus. The curriculum lists momentum alongside value and bubbles as market anomalies that behavioral finance is invoked to explain. Factor investing thus contains a live internal contradiction: value and momentum, both empirically rewarded, point in opposite directions at the same moment. See quality-vs-statistical-cheap and efficient-market-hypothesis.

SourcesCopy Anchor Link

• textbooks/markdown/investment-textbooks-pdfs__CFA LV1 2025 - Volume 09 - Portfolio Management.md
• investor-letters/GdnetGuruArticles/Letters-Markdown/What Has Worked In Investing (Christopher Browne).md