How Do Taxes Affect Income Distribution?
Inequality and poverty
What you will learn
- Progressivity depends on the share of income paid, not the cash amount alone.
- Apply the model to an original scenario and justify its limits.
Essential definitions
- Progressive tax
- A tax whose average rate rises as income rises.
- Regressive tax
- A tax whose average rate falls as income rises.
- Proportional tax
- A tax with a constant average rate as income rises.
- Marginal tax rate
- The proportion of an additional unit of taxable income paid in tax.
- Average tax rate
- Total tax paid as a proportion of income.
Classify taxes before comparing burdens
Direct taxes are imposed on income or wealth, such as income, company, property or inheritance taxes. Indirect taxes are imposed on expenditure, such as sales taxes and excise duties. Buyers and sellers may share an indirect tax's economic burden depending on how they respond to prices.
A progressive tax takes a larger income share from richer households. A proportional tax takes the same share; a regressive burden takes a larger share from poorer households. A richer person can pay more money under any of these patterns. Compare percentages of income, using a consistent period, rather than cash payments alone.
Understand the marginal and average rates
The marginal rate is tax on an additional unit of taxable income. The average rate is total tax ÷ total income × 100. A banded income tax applies each rate to the income within its band. Entering a higher bracket does not normally apply that rate to all earlier income.
The marginal rate affects the extra financial reward to work. The average rate describes the total burden. A uniform sales-tax rate can still be regressive relative to income if poorer households spend a larger fraction of their income on taxed purchases. Exemptions, rebates and transfers can alter the final pattern.
Evaluate the whole package
Progressive taxes can narrow disposable-income inequality and finance access to services. High rates may also encourage avoidance or change work and investment choices. Responses depend on enforcement, alternatives and whether people prefer additional income or leisure.
A tax funding effective healthcare can have a different overall distributional effect from the same tax funding services mainly used by richer households. State the fairness criterion: ability to pay, equal treatment, opportunity or protection of basic needs. Simplicity and predictable administration matter too. The following HL lesson applies these distinctions to tax-band and sales-tax arithmetic.
Apply and evaluate
- Examine taxes and benefits together; compare fairness, efficiency, revenue reliability and administration.
Common misconceptions
- A higher amount of tax paid does not necessarily mean a progressive tax.
Knowledge check
Does a constant tax share become progressive because richer people pay more units?
Real-world application
Poverty lines depend on a PPP vintage
5 June 2025: The World Bank’s June 2025 update set the international extreme-poverty line at $3.00 per person per day in 2021 PPP international dollars, replacing $2.15 in 2017 PPP dollars.
The change is not an ordinary market-exchange-rate conversion. PPP data and the national poverty lines underlying the benchmark changed. Comparing poverty counts across releases requires a consistent method; a statistical revision is not itself proof that living conditions suddenly worsened.
World Bank, June 2025 update to global poverty lines ↗Historical evidence checked 9 October 2026. The model interpretation is an original teaching application.
What to remember
Progressivity depends on the share of income paid, not the cash amount alone. Distinguish marginal from average rates and assess taxes alongside the services they finance.
Completion is your own reflection on learning, not a test score. Syllabus references: 3.4.10, 3.4.11, 3.4.12.
Sources and applications
Lessons in this section
- What Is Economic Inequality?
- How Do Lorenz Curves and Gini Coefficients Work?
- How Do We Draw a Lorenz Curve from Quintiles? · HL
- How Is Poverty Measured?
- Why Does Inequality Persist?
- How Do Taxes Affect Income Distribution?
- How Are Income Tax and Sales Tax Calculated? · HL
- How Can Transfers and Public Services Reduce Poverty?
- How Can Policy Support Incomes and Fair Access to Work?
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