What percent of the population is over 18? The younger working-age population, ages 18 to 44, represented 112.8 million persons (36.5 percent). The older working-age population, ages 45 to 64, made up 81.5 million persons (26.4 percent). Finally, the 65 and over population was 40.3 million persons (13.0 percent). How many US citizens are in […]