Beta is a measure of the volatility of a given stock relative to the overall market, usually the S&P 500.  Beta describes the sensitivity of an instrument to broad market movements.  A beta above 1 is more volatile than the overall market, while a beta below 1 is less volatile.  Securities with betas of zero generally move independently of the overall market.  And finally, stocks with negative betas tend to move in the opposite direction relative to the broader market.  When the S&P tumbles, stocks with negative betas will move higher, and vice versa.

• A beta of 2.50 represents stock price movement that is 150% more volatile than the S&P 500 Index.
• A beta of 1.00 represents stock price movement that has the same volatility as the S&P 500 Index.
• A beta of 0.50 represents stock price movement that is half as volatile as the S&P 500 Index.
• A beta of -0.50 represents stock price movement that is half as volatile of the S&P 500 Index, but the stock price tends to move in the opposite direction.