# Income distribution and equity

> IB Economics SL · IB Diploma Programme Economics SL
> Source: https://www.owlsprep.com/study/ib-economics-sl-u3-income-distribution-and-equity/

This subtopic explores how income is distributed across economies, distinguishes the key concepts of equity and equality, covers common measures of inequality and poverty, and evaluates government policies to promote more equitable outcomes, a frequent exam essay topic.

**Prerequisites:** [Core macroeconomic objectives](https://www.owlsprep.com/study/ib-economics-sl-u3-macroeconomic-objectives/)

## Learning objectives

- Distinguish between the concepts of equity and equality in income distribution
- Calculate and interpret measures of income inequality including the Lorenz curve and Gini coefficient
- Distinguish between absolute and relative poverty
- Evaluate the effectiveness of government policies to reduce income inequality and promote equity

## Equity vs Equality: Core Distinctions

The most commonly tested foundational concept on this topic is the difference between equity and equality, which students frequently conflate. Equality is a descriptive term for equal income distribution, while equity is a normative term referring to fairness of distribution.

**Equity** — A normative concept referring to the fairness of income distribution. Generally, equity means income distribution aligned with individual contribution, effort, or need, rather than strictly equal allocation.

*Example:* A system that rewards longer work hours with higher income is often considered equitable even if it is not equal.

**Equality** — A descriptive concept referring to an identical distribution of income across all individuals or households in an economy, with no variation in income.

**Worked example:** Country X gives every working adult an annual income of \$50,000, regardless of job role, hours worked, or skill level. Country Y allows incomes to range from \$25,000 for entry-level work to \$130,000 for specialized skilled work. Identify which country has more equality and which is more widely considered equitable, justifying your answer.

1. Step 1: Identify equality: Country X has complete income equality, as all working adults earn the exact same income.
2. Step 2: Analyze equity: Most frameworks judge Country Y as more equitable, because incomes reflect individual effort, skill, and contribution to the economy.
3. Step 3: Conclusion: Country X has more equality, while Country Y is more likely to be considered equitable.

> **Exam tip:** This distinction is almost always the first marking point in essays on this topic. Always define both terms explicitly to earn full marks.

## Measuring Inequality: Lorenz Curve and Gini Coefficient

Economists use two standard measures to compare income inequality across countries or over time. Both compare the actual distribution of income to a benchmark of perfect equality.

**Lorenz Curve** — A graph that plots the cumulative share of total income against the cumulative share of the population, ordered from poorest to richest. A 45-degree line represents perfect equality.

**Gini Coefficient** — A numerical measure of inequality that ranges from 0 (perfect equality, all income equal) to 1 (perfect inequality, one person holds all income). Lower values mean more equal distribution.

*Notation:* G

**Worked example:** Country A has a Gini coefficient of 0.31, Country B has a Gini coefficient of 0.47. Which country has higher income inequality? Explain how their Lorenz curves would compare.

1. Step 1: Recall the Gini coefficient scale: 0 = perfect equality, 1 = perfect inequality, so higher values mean higher inequality.
2. Step 2: Compare the values: 0.47 > 0.31, so Country B has higher income inequality.
3. Step 3: Lorenz curve comparison: The further a Lorenz curve lies below the 45-degree line of perfect equality, the higher the inequality. Country B's Lorenz curve will be further below the 45-degree line than Country A's.

> **Exam tip:** If asked to draw a Lorenz curve in Paper 1, always clearly label the 45-degree line as the line of perfect equality.

## Poverty: Absolute vs Relative

Poverty is closely linked to income inequality, and IB exams regularly test the distinction between two common measures of poverty: absolute and relative.

**Absolute Poverty** — Poverty measured against a fixed income threshold below which individuals cannot afford basic needs (food, shelter, clothing). The threshold does not change with average national income.

**Relative Poverty** — Poverty measured relative to the median income of a society, usually defined as income below 50% or 60% of the national median. It measures exclusion from average living standards.

**Worked example:** A country defines absolute poverty as income below \$2.15 per person per day, and relative poverty as income below 50% of the national median income of \$16 per day. A household earns \$5 per person per day. Is this household in absolute poverty, relative poverty, both, or neither?

1. Step 1: Compare to absolute poverty threshold: \$5 > \$2.15, so the household is not in absolute poverty.
2. Step 2: Calculate the relative poverty threshold: 50% of \$16 = \$8 per day.
3. Step 3: Compare to relative threshold: \$5 < \$8, so the household is in relative poverty. Final answer: relative poverty only.

## Government Policies to Promote Equity

Evaluation of policies to reduce inequality and promote equity is the most common extended response question on this topic. The main policies used are listed below:

- **Progressive taxation**: Higher income earners pay a higher percentage of their income in tax, reducing after-tax income inequality.
- **Transfer payments**: Government payments to low-income households (e.g., unemployment benefits, child benefits) that increase their disposable income.
- **Public service provision**: Free access to public education and healthcare improves upward mobility and reduces lifetime inequality.
- **Minimum wage**: A legal wage floor to boost incomes for low-skilled workers and reduce working poverty.

**Worked example:** Evaluate the use of progressive income taxation to reduce income inequality.

1. Step 1: Explain how it works: Progressive taxation takes a larger share of income from high earners, reducing their after-tax income. Revenue can fund transfer payments to low-income households, narrowing the income gap.
2. Step 2: Outline advantages: It directly reduces disposable income inequality, is relatively easy to administer in developed economies, and funds welfare programs that reduce poverty.
3. Step 3: Outline disadvantages: Very high marginal tax rates can create disincentives to work and invest, reducing overall economic output. They can also encourage tax avoidance and evasion by high earners.
4. Step 4: Conclusion: Progressive taxation is an effective tool for reducing inequality when designed with moderate tax rates that balance equity goals and economic efficiency.

> **Exam tip:** For 15-mark evaluation questions, always include at least one advantage, one disadvantage, and a final concluding judgment to reach the highest mark band.

## Common pitfalls

- **Wrong:** Confusing equity and equality, using the terms interchangeably in an essay response.
  - Why it fails: Examiners explicitly test this core distinction, and you will lose marks for failing to clarify it.
  - Correct: Define both terms early in your response, and explicitly state the difference between the two concepts.
- **Wrong:** Interpreting a higher Gini coefficient as meaning more equal income distribution.
  - Why it fails: Students often mix up the order of the 0 to 1 scale for the Gini coefficient.
  - Correct: Remember: Gini = 0 is perfect equality, 1 is perfect inequality, so a higher number always means more inequality.
- **Wrong:** Claiming relative poverty only exists in high-income developed countries.
  - Why it fails: Relative poverty is measured against a country's own median income, so it exists wherever there is any income inequality.
  - Correct: Recognize that both absolute and relative poverty can exist in low, middle, and high-income countries.
- **Wrong:** Stating that a higher minimum wage always reduces income inequality.
  - Why it fails: If the minimum wage is set far above the equilibrium wage, it can increase unemployment for low-skilled workers, worsening inequality.
  - Correct: Evaluate both effects: a moderate minimum wage reduces inequality, but an excessively high minimum wage may have the opposite effect.

## Cheatsheet

| Concept | Key Definition | Exam Note |
| --- | --- | --- |
| Equity | Fairness of income distribution | Normative, not the same as equality |
| Equality | Equal distribution of income | Descriptive, does not guarantee fairness |
| Gini Coefficient | 0 = perfect equality, 1 = perfect inequality | Higher value = more inequality |
| Lorenz Curve | Graph of cumulative income vs population | Further from 45° line = more inequality |
| Absolute Poverty | Fixed threshold for basic needs | Threshold does not change with average income |
| Relative Poverty | Below 50-60% of median income | Exists wherever there is income inequality |
| Progressive Tax | Higher income = higher tax rate | Reduces after-tax income inequality |
| Transfer Payments | Government payments to low-income households | Increases disposable income for poor households |

## What's next

Understanding income distribution and equity is a core part of macroeconomics, linking to broader discussions of macroeconomic objectives, the trade-off between equity and efficiency, and the role of government intervention in the economy. This topic regularly appears as an extended response essay in Paper 1, so it is important to master measurement and policy evaluation before moving on to related topics. The concepts you learn here also form a foundation for understanding inequality and poverty in development economics.

- [Fiscal and Monetary Policy](https://www.owlsprep.com/study/ib-economics-sl-u3-fiscal-and-monetary-policy/)
- [Supply-side policies](https://www.owlsprep.com/study/ib-economics-sl-u3-supply-side-policies/)
- [Economic growth](https://www.owlsprep.com/study/ib-economics-sl-u3-economic-growth/)

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