Over the next 30 years, the proportion of the world's population over age 60 will nearly double, from 9 percent to 16 percent. This is due to a sharp drop in the birth rate and an increase in life expectancy. As Figure II shows, almost 30 percent of the population in industrialized Organization for Economic Cooperation and Development (OECD) countries will be over age 60 by 2030. The population of the United States is still young compared with those of most European countries, but the proportion of people over age 60 in the U.S. will increase from 17 percent to 28 percent in the next 30 years.