Gini Index
Gini Index
Quick Definition
The Gini Index (also called the Gini coefficient) is a statistical measure of income or wealth inequality in a population. It ranges from 0 to 1 (or 0 to 100 on the percentage scale). A score of 0 means perfect equality where everyone has the same income. A score of 1 (or 100) means perfect inequality where one person has all the income and everyone else has nothing. Real-world societies fall between these extremes.
What It Means
The Gini Index answers a simple question: how evenly distributed is income (or wealth) in this society? It was developed by Italian statistician Corrado Gini in 1912 and remains the most widely used measure of economic inequality in the world. The World Bank, IMF, OECD, and UN all report Gini coefficients as a standard economic indicator.
Rising Gini coefficients within a country indicate growing inequality. Falling coefficients suggest movement toward more equal distribution. Cross-country comparisons reveal structural differences in how economies distribute the gains from economic growth.
How the Gini Index Is Calculated: The Lorenz Curve
The Gini Index is derived from the Lorenz Curve, a graph that plots cumulative income share against cumulative population share:
- X-axis: Cumulative share of population (from poorest to richest), 0% to 100%
- Y-axis: Cumulative share of income received, 0% to 100%
- Line of perfect equality: A 45-degree diagonal where the bottom 20% earn 20%, the bottom 50% earn 50%, and so on
- Lorenz Curve: The actual distribution, which bows below the diagonal
Gini = Area between Lorenz Curve and the line of equality / Total area below the diagonal
The further the Lorenz Curve bows below the equality line, the higher the Gini and the greater the inequality.
Global Gini Index Comparison (Income, Latest Available)
| Country | Gini Index | Inequality Level |
|---|---|---|
| Slovakia | 23 | Very low inequality |
| Sweden | 27 | Very low inequality |
| Germany | 32 | Low inequality |
| France | 32 | Low inequality |
| Canada | 33 | Low to moderate |
| Australia | 34 | Moderate |
| United Kingdom | 35 | Moderate |
| India | 35 | Moderate |
| China | 38 | Moderate to high |
| United States | 39 | Moderate to high |
| Mexico | 46 | High inequality |
| Brazil | 52 | Very high inequality |
| South Africa | 63 | Extreme inequality (among highest globally) |
Source: World Bank GINI Index data, latest available estimates (varies by country, 2021 to 2024).
US Gini Index Trend
The U.S. Census Bureau released the 2024 Gini Index in September 2025 as part of its annual Income in the United States report. The household income Gini was 0.488 in 2024, up slightly from 0.485 in 2023.
| Year | US Gini (Income) | Trend |
|---|---|---|
| 1967 | 0.399 | Reference point |
| 1980 | 0.403 | Beginning to rise |
| 1990 | 0.428 | Significant increase |
| 2000 | 0.462 | Continued rise |
| 2007 | 0.469 | Pre-financial crisis peak |
| 2010 | 0.469 | Recession impact |
| 2019 | 0.478 | Highest since WWII |
| 2020 | 0.488 | COVID impacts |
| 2022 | 0.488 | Post-pandemic |
| 2023 | 0.485 | Slight decline |
| 2024 | 0.488 | Back to 2020 level |
Source: U.S. Census Bureau, Income in the United States: 2024 (Report P60-286, released September 2025) and FRED ALFRED series GINIALLRH.
The US has experienced rising income inequality over the past five decades, driven by technology-biased skill premiums, declining union membership, globalization, and capital income concentration. The 90th-to-10th percentile income ratio reached 12.61 in 2024, meaning households at the 90th percentile earned over 12 times what those at the 10th percentile earned.
Income Gini vs. Wealth Gini
Income and wealth inequality are related but distinct:
| Measure | US Gini (Recent) | What It Shows |
|---|---|---|
| Income Gini | ~0.488 (2024) | Annual earnings distribution |
| Wealth Gini | ~0.85 | Net worth distribution |
Wealth inequality is dramatically higher than income inequality. The top 1% of Americans hold roughly 32% of total wealth. The bottom 50% hold approximately 2%. Wealth compounds over generations through inheritance and investment returns, creating more persistent inequality than annual income.
Limitations of the Gini Index
| Limitation | Issue |
|---|---|
| Single-number summary | Different distributions can yield the same Gini. A Gini of 0.4 could describe many different income shapes. |
| Income vs. consumption | Income Gini may overstate practical inequality if lower-income households receive significant government transfers and benefits. |
| Pre- vs. post-tax | Market income Gini is higher than disposable income Gini (after taxes and transfers). |
| Does not show where inequality occurs | High Gini could reflect a gap between the middle and the rich, or between the poor and the middle. |
| Excludes non-monetary wellbeing | Health, leisure, and public services are not captured. |
Factors That Drive Inequality
| Factor | Effect on Gini |
|---|---|
| Skill-biased technological change | Technology boosts returns to high-skill workers, raising Gini |
| Globalization | Shifts manufacturing jobs abroad, reducing wages for low-skill domestic workers |
| Declining unionization | Reduces wage bargaining power of workers |
| Returns to capital vs. labor | When capital earns more than wages, wealth concentrates |
| Progressive taxation | Reduces post-tax income inequality |
| Social transfers | Government benefits reduce disposable income inequality |
| Education access | Better access reduces skill-wage premium disparities |
Common Mistakes to Avoid
- Treating Gini as a complete picture: The Gini Index is a summary statistic. Two countries with the same Gini can have very different income distributions. Always look at percentile ratios and income shares for a fuller picture.
- Comparing Gini across different methodologies: The Census Bureau uses money income, while the World Bank uses consumption or income depending on the country. Cross-country comparisons should use the same data source and methodology.
- Confusing income Gini with wealth Gini: Income Gini for the US is around 0.488. Wealth Gini is around 0.85. These are very different numbers that measure very different things.
- Ignoring the effect of taxes and transfers: The US market income Gini is much higher than the post-tax, post-transfer Gini. The tax and transfer system reduces inequality, but less than in most European countries.
Key Points to Remember
- Gini Index ranges from 0 (perfect equality) to 1 (perfect inequality)
- Derived from the Lorenz Curve, which shows how far actual income distribution bows away from perfect equality
- Scandinavian countries (around 0.27 to 0.30) have the lowest Gini. Sub-Saharan African countries (around 0.55 to 0.65) have the highest.
- Wealth Gini (around 0.85) is far higher than income Gini (around 0.488). Wealth concentrates more than income.
- US income inequality has risen steadily since 1980 and is now among the highest of developed nations.
- Pre-tax vs. post-transfer Gini matters: US market income inequality is high, but taxes and transfers reduce it somewhat.
Frequently Asked Questions
Q: Is a high Gini Index always bad? A: Not necessarily. Context matters. Some inequality is inherent in market economies that reward innovation and risk-taking. Very high inequality (Gini above 0.45 to 0.50) is associated with reduced social mobility, higher crime, worse health outcomes, and political instability. Very low inequality (Gini below 0.25) may reflect excessive uniformity rather than genuine prosperity. Most economists consider a moderate Gini (0.25 to 0.35) consistent with both growth and broadly shared prosperity.
Q: Why does the US have higher inequality than Europe? A: Multiple structural factors contribute: less progressive taxation, weaker labor protections and lower union density, a less generous social safety net, higher returns to education in a technology-intensive economy, and lower mobility between income quintiles. The US also has higher pre-tax inequality partly due to its larger financial sector and technology industry concentration. European countries compress post-tax inequality more aggressively through social transfers.
Q: Does economic growth reduce inequality? A: The Kuznets Curve hypothesis from the 1950s predicted that inequality first rises then falls as countries develop. The evidence is mixed. Many rapidly growing countries (China, the US in the 1980s through 2000s) saw inequality rise alongside growth. Growth can reduce poverty by raising incomes at the bottom while simultaneously increasing inequality if gains concentrate at the top. Growth and inequality reduction are related but distinct policy challenges.
Q: What was the US Gini Index in 2024? A: The U.S. Census Bureau reported a household income Gini of 0.488 for 2024, up slightly from 0.485 in 2023. This is tied with 2020 and 2022 as the highest level recorded since the Census began tracking the measure in 1967. Source: Census Bureau Report P60-286, released September 2025.
Related Terms
Globalization
Globalization is the integration of economies, cultures, and populations across borders through trade, investment, technology, and migration. Despite rising tariffs and US-China decoupling, global trade hit record levels in 2025.
Capital
Capital is money or assets that are deployed to generate more wealth — distinguishing itself from income spent on consumption by being invested or used productively to create future economic value.
Comparative Advantage
Comparative advantage is the economic principle that individuals, companies, or countries should specialize in producing what they can produce at the lowest opportunity cost, even if another party is better at producing everything, forming the basis for mutually beneficial trade.
Economies of Scale
Economies of scale occur when a company's cost per unit decreases as output increases, giving larger producers a structural cost advantage over smaller competitors and creating a powerful barrier to entry.
Externality
An externality is a cost or benefit imposed on third parties who are not part of an economic transaction, such as pollution from a factory (negative) or vaccination reducing disease spread (positive). The social cost of carbon is estimated at $172-284 per ton in 2026 research.
Inflation
Inflation is the rate at which the general price level of goods and services rises over time, reducing the purchasing power of money and making financial planning essential for preserving real wealth.
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