What have been the trends in income inequality since 1980?

Over the years, economic growth has raised incomes in absolute terms; the entire distribution of income has been moving upward. But, the distribution of income by quintiles has become more unequal since 1980. In the lowest quintile, total before-tax income was 4.3 percent in 1980 but dropped to 3.1 percent in 2015. The income share received by the highest 20 percent rose from 43.7 percent in 1980 to 51.1 percent in 2015.