The capital asset pricing model (CAPM) is a theoretical framework that attempts to explain the relationship between risk and return for long-term investments. It is a key concept in modern portfolio theory and is widely used by financial professionals to estimate the required return for an investment asset.

Key Assumptions of CAPM:

• Random walk theory: Assumes that asset returns are random and independent of previous returns.
• Efficient market hypothesis (EMH): Assumes that all available information about an asset is already reflected in its price.
• No-arbitrage condition: Assumes that there are no opportunities to arbitrage (take advantage of price discrepancies).
• Risk-free rate: Assumes the existence of a risk-free asset with a known return.
• Beta: Assumes that the asset’s beta (sensitivity to market movements) is a reliable measure of its risk.

Formula for CAPM Return:

r = rF + β(rM - rF)

where:

• r: Expected return on the asset
• rF: Risk-free rate of return
• β: Asset’s beta
• (rM – rF): Market risk premium

CAPM Implications:

• Higher risk assets have higher expected returns: Assets with higher beta coefficients are expected to have higher returns.
• Risk-free rate and market risk: The risk-free rate and market risk premium are key factors in determining asset returns.
• Portfolio diversification: Diversification across assets with different betas can reduce overall portfolio risk.
• Systematic risk: CAPM cannot explain random fluctuations in asset returns, only systematic risk.

Criticisms of CAPM:

• Data dependence: CAPM relies on historical data to estimate beta and expected returns, which can be unreliable.
• Lack of theoretical foundation: CAPM lacks a solid theoretical foundation and some aspects are ad hoc.
• Market efficiency assumptions: CAPM assumes that markets are efficient, which may not always be true.

Overall, CAPM is a powerful tool for understanding the relationship between risk and return. However, it has limitations and should not be used in isolation.