Between 1900 and 1940, mortality rates in the United States fell 40 percent. How much did clean water matter? Harvard economist David Cutler and Stanford professor of medicine Grant Miller conducted a remarkable analysis, published in 2005, teasing out the impact of the new water treatment methods on the most dramatic reduction in death rates in U.S. history. By 1936, they conclude, simple filtration and chlorination of city water supplies reduced overall mortality in U.S. cities by 13 percent. Clean water cut child mortality in half.
