Beta is the measure of how volatile a stock is compared to the broader market or a benchmark index. A beta higher than 1 implies that it is more volatile, less than 1 but still positive implies less volatility, and a negative value implies it behaves opposite to the benchmark. For example, a beta of 1.25 indicates that the stock’s movements have been 25% greater, on average, than those of the index. Instituting a screen of a beta of less than 0.67 means the companies included have had price movements that have been less than two-thirds as large as those of the S&P 500.