CAPM calculates the expected return of an investment based on its risk relative to the market. It's the foundation of modern portfolio theory.
Risk-free rate = 5%, market return = 10%, stock beta = 1.2. Expected return = 5% + 1.2 × (10% - 5%) = 11%.
CAPM says higher risk (beta) should be compensated with higher expected returns. If a stock's actual return exceeds CAPM's prediction, it's generating alpha (excess return).
In March 2024, the 10-year Treasury yield (risk-free rate) was ~4.2%, and the long-term equity risk premium was ~5%. For a stock like Microsoft with a beta of ~0.9, CAPM gives: 4.2% + 0.9 × 5% = 8.7% expected return. If MSFT actually returned 15% over the next year, it generated 6.3% alpha above what CAPM predicted for its risk level.
For a high-beta stock like Tesla (beta ~2.0), CAPM predicts: 4.2% + 2.0 × 5% = 14.2% expected return. Higher expected return, but also much more volatility to endure.
| Beta | Expected Return | Example | Risk Profile |
|---|---|---|---|
| 0.5 | 6.7% | Utilities ETF | Low volatility |
| 1.0 | 9.2% | S&P 500 index | Market risk |
| 1.5 | 11.7% | Small-cap growth | Above-market risk |
| 2.0 | 14.2% | Tesla, leveraged ETFs | Very high risk |
💡 Pro Tip: Use CAPM to evaluate fund managers. If a mutual fund returned 12% with a beta of 1.3, and CAPM predicted 11.7% for that beta, the fund only added 0.3% alpha — barely beating its risk-adjusted benchmark. A fund returning 12% with beta 0.8 would have much more impressive alpha.
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Try Position Size Calculator →Is CAPM still used by professionals?
Yes, but with modifications. While academics debate its accuracy, investment banks and corporate finance teams still use CAPM to estimate the cost of equity. Practitioners often combine CAPM with other models like the Fama-French three-factor model for better estimates.
What's a typical expected market return?
Most analysts use 8-10% for the S&P 500 expected return, based on historical averages. For the risk-free rate, the 10-year US Treasury yield is standard. As of recent years, this has ranged from 2% to 5% depending on Federal Reserve policy.
What are CAPM's main weaknesses?
CAPM assumes a single factor (market risk) explains returns, which is too simplistic. It also assumes investors are rational, markets are efficient, and beta is stable — none of which hold perfectly in practice. Despite this, it remains widely used due to its simplicity.
Is CAPM still relevant in modern investing?
CAPM is widely taught and used in corporate finance for calculating cost of equity, but it has known limitations. It assumes markets are efficient and beta fully captures risk — both questionable assumptions. In practice, most analysts use CAPM as a starting point and supplement with multi-factor models like Fama-French.
What is the equity risk premium?
The equity risk premium is the expected excess return of stocks over the risk-free rate — the compensation investors demand for taking on stock market risk. Historically, the US equity risk premium has been about 4-6%. This is a key input in CAPM and one of the most debated numbers in finance.
Why does CAPM sometimes give unrealistic results?
CAPM can produce negative expected returns for low-beta stocks during periods of inverted risk-free rates. It also treats beta as the sole risk measure, ignoring size, value, and momentum factors that research shows affect returns. Use CAPM estimates as one data point among many, not as gospel.