Beta is a measure of the market risk, or methodical risk, of a particular privacy or portfolio. Systematic risk defines any risk that influences the value of a huge number of assets. Beta measures a security's return over time relative to the overall market. (Note that market return is mostly measured by Standard & Poor's 500 Composite Stock Index or the Dow Jones 30 Industrials.) The higher the beta, the riskier, or the more volatile, is the stock or portfolio. Beta is commonly used to analyze the risk of equality common funds by showing the volatility of a fund relative to the market as a whole (as measured by the Standard & Poor's 500 Index of the most widely held stocks). A common fund with a beta of 1.0 would have returns that match those of the S&P 500. A common fund with a beta greater than 1.0 is more volatile, or riskier, than the market. A common fund with a beta less than 1.0 is not as risky, volatile, or as the market.