According to the U.S Census Bureau, median household incomes ranged from $33,000 in West Virginia to $57,000 in New Hampshire, with an overall national median of $46,000 and 42 percent of households having two or more income earners. Using purchasing power parity exchange rates, these income levels are similar to those found in other postindustrial nations such as Switzerland ($54,000) and the United Kingdom ($39,000). In 2005, the median income for an individual age twenty-five or older in the labor force was $32,000 while the median income per household member was $24,000 between 12.6 and 13.3 percent of Americans were below the federally designated poverty line. Income inequality has increased since the 1970s,although the standard of living has increased for nearly all classes.The share of income held by the top 1 percent has increased considerably while the share of income of the bottom 90 percent has fallen, with the gap between the two groups being roughly as large in 2005 as in 1928.According to the standard Gini index, income inequality in the U.S. is higher than in any European nation. Some economists, such as Alan Greenspan, see rising income inequality as a cause for concern.

While American social classes lack defined boundaries, sociologists point to social class as a crucial societal variable. Occupation, educational attainment, and income are used as the main indicators of socioeconomic status. Dennis Gilbert of Hamilton College has proposed a system, adapted by other sociologists, with six social classes: an upper, or capitalist, class consisting of the wealthy and powerful (1%), an upper middle class consisting of highly educated professionals (15%), a middle class consisting of semiprofessionals and craftsmen (33%), a working class consisting of clerical and blue-collar workers who conduct highly routinized tasks (33%), and two lower classes—the working poor (13%) and a largely unemployed underclass (12%). Though the American Dream, or the perception that Americans enjoy high social mobility, played a key role in attracting immigrants to the United States, particularly in the late 1800s, some analysts have found the U.S. to have relatively low social mobility compared to Western Europe and Canada.