The U.S. has a progressive income tax system. Therefore, the rate of tax increases as taxable income increases. The purpose of imposing progressive taxes is to reduce the tax incidence of people with a lower ability to pay taxes, as these taxes shift increasingly to those with a higher ability-to-pay. Thus, the bulk of tax revenue is in high-income households.

Statistics just released by the IRS show that the top 1% of households received more than 20% of adjusted gross income in 2014 while paying almost 40% of income taxes. Less than 4% of income tax is paid by the bottom 50% of households. Federal tax rates in 2015 varied from 10% to 39.6%.