CAPM Guide
CAPM is a mathematical model that describes the relationship between systematic risk and expected return for assets, particularly stocks.
Key Concepts
- Risk-Free Rate: The return of an investment with zero risk, usually govt bond yields.
- Beta (β): Measure of an investment's sensitivity to market volatility and movements.
- Market Risk Premium: The extra return expected from the market over the risk-free rate.
- Systematic Risk: Market-wide risks like inflation that cannot be diversified away.
- Unsystematic Risk: Company-specific risks that can be eliminated through diversification.
- Security Market Line: Graphical representation of CAPM showing return vs. Beta.
The Core CAPM Formula
The CAPM formula states that expected return is equal to the risk-free rate plus the Beta times the market risk premium.
This suggests investors must be compensated for the time value of money (risk-free rate) and for taking on systematic market risk (premium adjusted by Beta).
Understanding Beta
Beta is the most critical variable. A stock with a Beta of 1.2 is 20% more volatile than the market, requiring a higher return to justify the risk.
Conversely, a Beta of 0.5 suggests lower risk and lower expected returns. Analysts use Beta to gauge how an asset impacts a portfolio's risk profile.
Applications in Finance
For companies, CAPM is the primary method for calculating the "Cost of Equity," which is a key input for WACC and project valuations.
If a company's projects don't return at least what CAPM predicts for its risk level, it is effectively destroying shareholder value in the long run.
Real-World Critique
While theoretically sound, CAPM has limitations. It assumes market efficiency and that Beta is a perfect measure of risk based on historical data.
In reality, historical Beta may not predict future volatility perfectly, leading some analysts to supplement it with multi-factor models.
Foundational Theory
Despite its simplifications, CAPM remains the foundation of modern portfolio theory, offering a logical framework for risk-reward trade-offs.
Understanding CAPM is essential for justifying investment choices and setting realistic performance benchmarks in a competitive market.