Evidence from Developed CountriesHistorical evidence from now-developed low-mortality countries at a time when their mortality rates were higher than those in high-mortality countries today strongly suggests that information, education, and awareness campaigns improved hygiene and reduced mortality.Samuel Preston studied the early twentieth-century United States (Preston 1996). In 1900, life expectancy in the United States was 48 years, much lower than, for example, India’s life expectancy of 60 years in 2000. Life expectancy in the United States increased rapidly during the twentieth century, to 78 years. This was not due to curative medicine, as the bulk of the declines in infectious diseases came before effective medical treatment became available. Nor was it due to improved nutrition. The United States in 1900 was already a well-fed countrywith calorie consumption per equivalent adult higher than it was a hundred years later.The main reason for the increase in life expectancy was the improved disease environment,resulting from a number of factors: improved sanitation, a cleaner water supply (Cutler andMiller 2005), immunization, and improved hygiene
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