Annual Report of the White House Task Force on the Middle Class

One view of the implicit social contract that has defined the American middle class is that as the economy expands, the living standards of middle-class families will improve. Between 1947 and 1979, real median family income grew at an annual rate of 2.4 percent, which amounts to about a doubling of real income over this period; that contract was fully operative in the [those] few decades. After 1979, however, this trend decelerated significantly, as real median
family income grew only 0.4 ...