The rate of tax can be expressed in two different ways; the marginal rate expressed as the rate on each additional unit of income or expenditure (or last dollar spent) and the effective (average) rate expressed as the total tax paid divided by total income or expenditure. In most progressive tax systems, both rates will rise as the amount subject to taxation rises, though there may be ranges where the marginal rate will be constant. Usually, the average tax rate of a tax payer will be lower than the marginal tax rate.