Explainer, in Risk & Portfolio Construction
Alpha
Jensen's alpha: α = R_p − [R_f + β(R_m − R_f)], where R_p is portfolio return, R_f the risk-free rate, R_m the market return, and β the portfolio's exposure to the market factor. Generalizes to multi-factor models — Fama-French, Carhart, AQR-style — where alpha is residual excess return after subtracting all priced-factor exposures.
1 question. Published May 10, 2026. By AI Fin Hub Research.
Definition
Alpha
Jensen's alpha: α = R_p − [R_f + β(R_m − R_f)], where R_p is portfolio return, R_f the risk-free rate, R_m the market return, and β the portfolio's exposure to the market factor. Generalizes to multi-factor models — Fama-French, Carhart, AQR-style — where alpha is residual excess return after subtracting all priced-factor exposures.
Why it matters
Returns without context are meaningless. A 20% strategy in a 25% market is negative alpha at beta 1; the same 20% with beta 0.3 is roughly 13% alpha. Allocators pay for alpha and refuse to pay for beta. Most strategies marketed as alpha are mostly disguised beta.
How it works
Run a regression of strategy excess returns on benchmark excess returns. The intercept is alpha; the slope is beta. Multi-factor: regress on (market, size, value, momentum) or your chosen factor set. Significance test the intercept — if its t-stat is below 2, the alpha is statistically indistinguishable from zero on that sample.
Example
Long-only equity strategy, 3 years, monthly
Strategy annualized return
14%
Market annualized return
11%
Risk-free rate
3%
Estimated β
0.95
Expected return at β=0.95
3 + 0.95 × (11 − 3) = 10.6%
Alpha
14 − 10.6 = 3.4%
Headline 14% looks great vs 11% market. Once beta is netted out, the alpha is 3.4% — still positive, but only a third of the apparent edge.
Key takeaways
Alpha without a defined factor model is rhetoric, not measurement.
Most strategies that claim alpha collapse to near-zero once a 4-factor model is applied.
Statistical significance of alpha matters more than the point estimate on short samples.
Related terms
Questions people ask next
Can alpha be negative?
Yes — and most actively managed funds produce negative alpha after fees. That's the empirical case for index investing.
Sources
- The Performance of Mutual Funds in the Period 1945-1964 , Journal of Finance (Jensen, 1968)
Keep the topic connected
- Learn Beta
Beta as factor sensitivity: what it measures, why a beta of 1 doesn't mean 'tracks the market', and the rolling-vs-static distinction to watch.
- Learn Sharpe Ratio
Sharpe ratio defined, when it lies (skew, fat tails, autocorrelation), and how to read a Sharpe number you didn't compute yourself.