Progressive Tax
A progressive tax is a tax in which the average tax rate increases as the taxable amount increases, so that higher-income individuals pay a larger share of their income in tax than lower-income individuals. Progressivity is a key feature of many personal income tax systems and is justified on grounds of vertical equity and the ability-to-pay principle. It is contrasted with proportional and regressive taxes.
Measurement
Progressivity can be measured in several ways. The average tax rate, the ratio of tax paid to income, rises with income under a progressive system. The marginal tax rate, the tax on an additional unit of income, exceeds the average rate, and it determines the incentive effects at the margin. The structure of marginal rates, called the rate schedule, may be graduated, with rates rising in steps, or continuous.
Summary measures of progressivity include the Kakwani index, which compares the concentration of tax payments with the distribution of income, and the Reynolds-Smolensky index, which measures the redistributive effect of the tax system. These measures allow comparisons across countries and over time, though they depend on the definition of income and on the treatment of transfers.
Design features
Progressive tax systems typically combine several features. A personal allowance or basic deduction exempts a threshold of income from tax, raising progressivity at the bottom. Graduated marginal rates apply higher rates to higher brackets of income. Credits and deductions may further differentiate treatment by family circumstances, housing, or other characteristics. Capital income may be taxed at different rates, often lower than labour income, which can reduce overall progressivity.
The design of these features involves trade-offs. Higher top rates raise revenue and increase progressivity but may discourage work, saving, and entrepreneurship, and may encourage tax avoidance. A broad base with moderate rates is often recommended to raise revenue efficiently, but it may be less progressive than a narrow base with high rates. The optimal design depends on the objectives of the tax system and on behavioural responses.
Justifications
Progressive taxation is justified on several grounds. The ability-to-pay principle holds that those with greater capacity to pay should contribute more. The diminishing marginal utility of income suggests that an additional dollar is worth less to a rich person than to a poor person, so that redistributing income through progressive taxes can raise total welfare, under certain assumptions. Vertical equity holds that unequal treatment of unequals is fair.
Progressive taxes also serve redistributive objectives, reducing inequality and funding transfers and public services that benefit lower-income households. Empirical research finds that progressive taxes and transfers substantially reduce measured inequality in most advanced economies, with the tax system and the transfer system together playing a larger role than either alone.
Criticisms and debates
Critics of progressive taxation argue that high marginal rates reduce incentives to work, invest, and innovate, potentially reducing growth. They point to the distortionary effects of high rates and to the potential for tax avoidance and emigration of high earners. Some argue that consumption taxes, which are typically regressive, are more efficient, and that redistribution, if desired, is better achieved through the spending side of the budget.
The empirical evidence on the growth effects of progressive taxation is mixed. The relationship between tax rates and economic performance depends on the structure of the tax system, on the use of revenue, and on the responsiveness of taxpayers. Modern analysis emphasises that the appropriate degree of progressivity depends on society's preferences for redistribution and on the efficiency costs of taxation, and that these trade-offs should be assessed with evidence rather than assumption.
The rate schedule and effective progressivity
The statutory rate schedule is only one determinant of actual progressivity. Deductions, exemptions, and credits shape the effective rate schedule, and the interaction of these provisions with the tax base determines how much tax different households pay. Broad deductions, such as those for mortgage interest or charitable contributions, tend to benefit higher-income households more, reducing effective progressivity. Refundable credits targeted at low-income households increase progressivity.
Effective progressivity also depends on the treatment of different income sources. If capital income is taxed at lower rates than labour income, the overall system is less progressive than the statutory rate schedule suggests, particularly since capital income is concentrated among higher-income households. The balance between taxing labour and capital is a central issue in tax design.
The tax mix
Overall progressivity depends on the whole tax system, not just the personal income tax. Consumption taxes, such as value-added taxes, are typically regressive relative to current income, though they may be proportional or progressive relative to lifetime income. Property taxes and wealth taxes can be progressive. Payroll taxes are often proportional or regressive.
The progressivity of the overall system therefore reflects the mix of taxes and the composition of revenue. Countries with broad consumption taxes and limited income taxation tend to have less progressive systems, while those with progressive income taxes and transfers have more. The design of the overall mix, and the use of revenue from different sources, determines the redistributive effect.
Redistribution and growth
The relationship between progressive taxation and growth is a longstanding subject of debate. Theory suggests that high marginal rates can reduce incentives to work, save, and invest, but the magnitude of these effects is contested. Empirical research finds that the growth effects of progressivity depend on the specific design, the level of rates, and the use of revenue, and that modest progressivity is unlikely to impose large efficiency costs.
The redistributive effect of progressive taxes can also support growth, by funding education and health investments that raise human capital, and by reducing inequality that can undermine social cohesion and political stability. The optimal degree of progressivity therefore depends on society's preferences for redistribution and on the efficiency costs of taxation, and it must be assessed with evidence on behavioural responses and on the use of revenue.