Personal income tax brackets
United States
For more details on this topic, see Income tax in the United States and Taxation in the United States
The progressive aspects of the Federal income tax rates in the United States have varied widely since 1913. For example, in 1954 the Congress imposed a Federal income tax on individuals, with the tax imposed in layers of 24 income brackets at tax rates ranging from 20% to 91% (for a chart, see Internal Revenue Code of 1954). As of 2006, there are six “tax brackets” ranging from 10% to 35% used to calculate the percentage of taxable income (of individuals) that must be paid to the United States Treasury. If taxable income falls within a particular tax bracket, the individual pays the listed percentage of income on each dollar that falls within that monetary range. For example, a person who earned $10,000 in 2006 would be liable for 10% of each dollar earned from the 1st dollar to the 7,550th dollar, and then for 15% of each dollar earned from the 7,551st dollar to the 10,000th dollar, for a total of $1,122.50. This ensures that every rise in a person’s salary results in an increase of after-tax salary. The Treasury Department in 2006 reported, based on Internal Revenue Service (IRS) data, the share of all federal taxes paid by taxpayers of various income levels. The data shows the progressive structure of the U.S. federal tax system that reduces the tax incidence of people with smaller incomes, as they shift the incidence disproportionately to those with higher incomes - the top 0.1% of taxpayers by income pay 17.4% of all federal taxes (earning 9.1% of the income), the top 1% pay 36.9% (earning 19%), the top 5% pay 57.1% (earning 33.4%), and the bottom 50% pay 3.3% (earning 13.4%).
-Wikipedia