In 2013, Eugene Fama and Kenneth French won the Nobel Prize in Economic Sciences. They revised the Capital Asset Pricing Model (CAPM), which simplified the estimation of how much return is required to justify an investment.
The CAPM calculates the expected return by comparing how much investors can expect to earn from investing in the market, such as the S&P 500, with the return on short-term government bonds. This difference, known as the market premium, is then multiplied by beta, which measures how a specific investment moves in relation to the overall market, to derive the expected return. William Sharpe, along with John Lintner and Jan Mossin, developed the CAPM based on Harry Markowitz’s portfolio theory. Sharpe later received the 1990 Nobel Prize in Economic Sciences, shared with Markowitz and Merton Miller, for their foundational work on risk and return.
Fama-French Three-Factor Model
Fama and French later revised the CAPM and introduced two additional factors in their Three-Factor Model, where market risk, the first factor, comes from the original CAPM. The model incorporates two further dimensions to calculate the required rate of return: the effect of company size, and the company’s book value relative to its stock price.
In their research, Fama and French found that smaller companies tended to have higher returns than larger ones. They incorporated this observation into the model as SMB (Small Minus Big). In this factor, the return of large companies is subtracted from that of small companies, which consistently showed positive values, indicating that returns for small companies were greater than those of large companies.
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