The Capital Asset Pricing Model (CAPM): Pricing Risk and Estimating the Cost of Equity
The Capital Asset Pricing Model (CAPM), developed by William Sharpe, John Lintner, and Jan Mossin in the 1960s, is one of the most foundational pillars of modern corporate finance and investment valuation. CAPM establishes the linear relationship between systematic risk and expected return for assets, particularly equities. It asserts that investors must be compensated in two ways: for the time value of money, and for assuming non-diversifiable systematic market risk.
The core formula of CAPM is: E(Ri) = Rf + βi × (Rm - Rf). Here, Rf is the risk-free rate, which compensates investors for locking up capital with zero default risk. (Rm - Rf) represents the Equity Risk Premium (ERP)—the excess return that the entire equity market yields over sovereign debt. Beta (βi) scales that equity premium based on how sensitive the specific stock is to overall market fluctuations.
In corporate finance, CAPM serves as the universal methodology for determining a corporation's Cost of Equity (Ke). When calculating the Weighted Average Cost of Capital (WACC) to discount future free cash flows in a Discounted Cash Flow (DCF) model, analysts use CAPM to find what return equity shareholders demand. If an investment project does not generate an Internal Rate of Return (IRR) higher than the CAPM expected return, it destroys shareholder value.
While CAPM remains the industry standard, modern financial practitioners also consider multi-factor extensions such as the Fama-French Three-Factor or Five-Factor models, which incorporate size, value, profitability, and investment factors. Nonetheless, CAPM's intuitive balance of risk-free yields, market premiums, and systematic beta ensures it remains the premier corporate valuation benchmark.