Middle class is defined as adults with household incomes between two-thirds and twice the national median, or between $40,000 and $120,000 today. In 1971, 61% of adults were middle class, 14% were upper class and 25% were lower class. Today, just 51% are middle class, 20% are now upper class, and 29% lower class. Even for the increased percentage in the lower class, real incomes are up 29% since 1971.