U.S. adult population 1971-2015. by income tier

This statistic shows the U.S. adult population from 1971 to 2015 by income tier. In 2015, about 121 million adult U.S. residents were part of the middle class. This study defined middle class income households as those with an income between 67 and 200 percent of the U.S. median household income, after adjustment for household size. Middle class income ranges from about 42,000 U.S. dollars to about 126,000 U.S. dollars per year for a three-person household.