 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.Tax policy is the mechanism through which market results are redistributed, affecting after-tax inequality.