The United States has the highest income inequality among comparable nations. The left-side graph depicts the US as having a favorable Gini coefficient (a measure of income inequality) without taxes. After taxes and government transfers are factored in, the US becomes highly unequal. One of the reasons for this trend is that, although the US uses progressive taxation, the tax rates are significantly lower than the international standard and social welfare programs are also much less generous.
–From The New York Times