Jensen Alpha

Jensen alpha is a measure of the returns that are attributable to the managers' ability to select security and time the market. In other words, it is the returns remaining after deducting what would have been attributable to beta returns (which do not require skill) and the risk-freerate.

Jensen Alpha 
ER[a] - RFR * (1-BETA) 
BETA * ER[b]) 

Jensen alpha is the difference between the return of the portfolio, and what the portfolio should theoretically have earned. Any portfolio can be expected to earn the risk-free rate (RF), plus the market risk premium (which is given by [Beta x (Market Portfolio Return - Risk-Free Rate)]. Anything remaining over and above is alpha.

Jensen Alpha In A Nutshell

Let us use this in an example. You are searching funds and find two that are the same return and other stats. Using the Jensen Alpha, you may be able to see which one is taking on less risk to obtain those returns compared to the other that may be using more risk to generate those returns. That means one may have greater volatility and many investor attempt to eliminate that aspect of the portfolio.

Alpha is the measure of return for a given equity, portfolio, or investment. This data point is what we want to maximize without increasing factors such as risk or cost. Jensen Alpha measures return but takes into account a risk-adjusted aspect of the alpha. Using this alpha will also utilize CAPM and take into account the product or portfolio beta number. Beta is the correlation to the underlying market and how it reacts, with a 1 being a lock step with the underlying.

Closer Look at Jensen Alpha

Everybody looks at returns and the factors that go into them individually, but we all are searching for the same. Less risk for greater returns. Jensen Alpha helps to take into account the risk aspect but that doesn’t mean it is the stopping point, but merely a directional indicator. Look at fundamentals and historical performance to gain a better understand and what you can expect going forward.