A statistical number that measures how a stock may fluctuate in price relative to a market index. If a stock has a beta of less than 1, it should move at a lower rate than the rest of the market. If it is 1, it should move at the same rate. If it is greater than 1, it should move up or down at a greater rate. Movements are proportioned percentage-wise and are compared to a market index such as the Dow Jones Industrial Average.