Jensen Alpha
Jensen Alpha measures the excess return a portfolio generates above or below what would be predicted by the Capital Asset Pricing Model (CAPM) given its beta, providing a theoretically grounded measure of the value added or destroyed by active fund management.
Developed by Michael Jensen in 1968, Jensen's Alpha (often simply called 'alpha' in the fund management context, though the term has broader usage) is the intercept term in the CAPM regression line. It represents the portion of a fund's return that cannot be explained by its exposure to systematic market risk. A positive Jensen Alpha indicates the fund manager generated returns above the CAPM-expected return — true value addition; a negative alpha indicates underperformance relative to what passive exposure to the market would have delivered for the same level of risk.
The formula embeds a key distinction from simple excess return. If the Nifty 50 returned 12% in a year, the risk-free rate was 7%, and a fund with a beta of 1.2 returned 14%, the CAPM-predicted return would be: 7% + 1.2 × (12% − 7%) = 7% + 6% = 13%. The Jensen Alpha is 14% − 13% = +1%, indicating the fund added 1% of genuine alpha after accounting for its higher market risk (beta > 1). Without CAPM adjustment, comparing the 14% fund return against 12% benchmark would suggest 2% alpha, but 1% of that is simply compensation for bearing 20% more systematic risk.
In Indian mutual fund evaluation, Jensen Alpha is used by institutional investors, financial planners, and analytical platforms to compare funds on a risk-adjusted basis that explicitly accounts for each fund's market sensitivity. It is particularly useful for comparing funds with different beta profiles — for example, a high-beta mid-cap fund vs. a low-beta large-cap fund cannot be compared meaningfully using raw alpha (excess return over benchmark alone).
The calculation requires the following data: fund's monthly or weekly returns over the evaluation period, corresponding benchmark returns, and the risk-free rate (typically the 91-day T-bill yield for the period). A linear regression of (Fund Return − Risk-Free Rate) on (Benchmark Return − Risk-Free Rate) yields beta as the slope and Jensen Alpha as the intercept.
Limitations include the assumption that beta is stable over time (it is not — betas shift with market conditions and portfolio changes), that the benchmark chosen is appropriate, and that the CAPM itself adequately describes expected returns (multi-factor models like the Fama-French three-factor or five-factor models capture additional risk premia). Despite these limitations, Jensen Alpha remains a widely referenced metric in academic and professional fund evaluation.
AMFI, Value Research, and Morningstar India publish alpha data for Indian mutual funds, though the methodology for calculation varies across platforms.