Jensen's Alpha — What is Alpha in Investing?
Definition of Jensen's Alpha. How it measures excess return above benchmark and what it means for portfolio manager evaluation.
Definition
Alpha (α), also known as Jensen's Alpha, is a measure of excess return on investment above what the CAPM (Capital Asset Pricing Model) predicts for a given level of risk (beta).
Simply put: alpha tells you how much more (or less) you earned than you should have, considering the risk you took.
Interpretation
- α > 0 — portfolio beat benchmark after adjusting for risk (manager added value)
- α = 0 — portfolio performed exactly as the model predicted
- α < 0 — portfolio underperformed benchmark (manager subtracted value)
Formula
α = Rp - [Rf + β × (Rm - Rf)]
Where:
- Rp = actual portfolio return
- Rf = risk-free rate
- β = portfolio beta
- Rm = market return (benchmark)
Example
Your portfolio earned 15%, market (S&P 500) 12%, risk-free rate 3%, portfolio beta 1.2.
α = 15% - [3% + 1.2 × (12% - 3%)]
α = 15% - [3% + 10.8%]
α = 15% - 13.8% = +1.2%
Your alpha is +1.2% — you earned 1.2% more than the model predicted for your risk level.
Why is alpha important?
Alpha is a key metric for evaluating:
- Fund managers — is the active fund worth higher fees?
- Your portfolio — do your decisions add value vs a simple index ETF?
Studies show that 80–90% of active funds generate negative alpha after fees. That's why many experts recommend passive investing (ETFs).
Alpha vs beta
- Beta = how much market risk you take
- Alpha = how much extra return you generate above that risk
Passive investors aim for beta = 1 and alpha = 0 (same results as market). Active investors seek positive alpha.
How Freenance can help?
Freenance can calculate your portfolio's alpha by comparing results with chosen benchmarks. Check if your investment decisions actually add value — or whether you should switch to a simpler ETF portfolio.
👉 Measure your portfolio's alpha with Freenance — freenance.io
Want full control over your finances?
Try Freenance for free