Correlated risk profiles move in concert when affected by the same set of stimuli. For example, there is substantial correlation between the Dow Jones Industrial Average (DJIA) and the Standard & Poor's (S&P) 500 Index because both are affected by the same factors. In contrast, uncorrelated risk profiles (e.g., a book of ocean marine business and a book of products liability coverage) react to entirely different stimuli. The combination of uncorrelated risk profiles results in lower combined volatility.