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The statistic shows the shares of household income of quintiles in the United States from 1970 to 2011. About 50 percent of the household income of private households in the U.S. are earned by the highest quintile, which are the upper 20 percent of the workers in 2011. Only 3.4 percent of the household income are earned, on the other hand, by the lowest quintile. The relation between the quintiles illustrates the income inequality in the United States.