Economics A-Z | Economist.com

Economics A-Z | Economist.com: "Beta Part of an economic theory for valuing financial securities and calculating the cost of capital, known as the capital asset pricing model, beta measures the sensitivity of the price of a particular asset to changes in the market as a whole. If a company's shares have a beta of 0.8 it implies that on average the share price will change by 0.8% if there is a 1% change in the market. There is a long-running debate about whether a beta calculated from a security's past relationship with the market actually predicts how that relationship will behave in future, leading some doubting economists to claim that beta is 'dead'."