Tax policy and economic inequality in the United States discusses how tax policy affects the distribution of income and wealth in the United States. Income inequality can be measured before- and after-tax; this article focuses on the after-tax aspects. Income tax rates applied to various income levels and tax expenditures (i.e., deductions, exemptions, and preferential rates that modify the outcome of the rate structure) primarily drive how market results are redistributed to impact the after-tax inequality. After-tax inequality has risen in the United States markedly since 1980, following a more egalitarian period following World War II.