The rate at which income over a certain amount is taxed. Although in general, graduated income taxes impose higher tax rates on higher incomes, the tax rate does not rise for each additional dollar earned. Rather, it rises by income brackets, and each tax rate applies only to income that falls in that bracket. For example, in 2002, the highest marginal federal tax rate was 38.5 percent, which for single taxpayers was imposed on income in excess of $54,000.
If two single people each earn $50,000, they will each pay the marginal tax rate that applies to $50,000.