Gini Coefficient — Smart Financial Analysis

Gini Coefficient Definition

Developed by Italian statistician Corrado Gini in 1912, the Gini coefficient quantifies the deviation of an income or wealth distribution from perfect equality. It equals twice the area between the Lorenz curve and the 45-degree line of perfect equality, normalized to a 0–1 scale.

A Gini of 0 means every person has identical income; a Gini of 1 means one person has all income. The metric is widely used by the World Bank, OECD, and national statistical agencies for policy analysis and international comparisons.

Gini Coefficient Interpretation

Below 0.25 indicates low inequality, typical of Nordic welfare states. 0.25–0.35 is moderate, common in many European and East Asian nations. 0.35–0.45 is high for developed nations — the US at 0.39 falls here. Above 0.50 indicates very high inequality, seen in South Africa (0.63), Brazil, and several Latin American countries.

Lorenz Curve

The Lorenz curve plots cumulative population share (x-axis) against cumulative income share (y-axis). The line of perfect equality is a 45-degree diagonal: if the bottom 50% of the population earned 50% of income, the curve would follow this line.

The further the Lorenz curve bows below the diagonal, the higher the inequality. The Gini coefficient equals the ratio of the area between the curve and the diagonal to the total area under the diagonal. This calculator visualizes your data's Lorenz curve alongside the perfect-equality line.

Gini by Country

South Africa (0.63) has the highest Gini among major economies, with the top 10% earning about 65% of income. Brazil, Namibia, and several Latin American nations also exceed 0.50. Sweden (0.27), Norway, and Denmark have among the lowest Gini coefficients globally, achieved through progressive taxation and strong social safety nets.

Japan (0.33) and many European nations fall in the 0.30–0.35 range. The United States at 0.39 is the most unequal among large developed economies, with inequality rising since the 1980s.

Income Inequality Trends

Global between-country inequality has fallen since 2000 as China, India, and other emerging economies grew. The global Gini has decreased from about 0.70 to 0.62. Within-country inequality has risen in many developed nations, including the US and UK.

Wealth inequality typically exceeds income inequality — the top 1% often hold a far larger share of wealth than income. Policy responses include progressive taxation, minimum wages, and social transfers, though effectiveness varies by context.

Gini Coefficient Limitations

The Gini coefficient does not show where inequality is concentrated — two distributions can have the same Gini but differ in whether inequality is in the middle or at the extremes. It is sensitive to outliers: a few very high incomes can raise Gini substantially. Different distributions (e.g., bimodal vs. unimodal) can yield similar Gini values.

For fuller analysis, complement Gini with the Palma ratio (top 10% to bottom 40%), percentile ratios (e.g., 90th/10th), or the Theil index. Gini also does not distinguish income from wealth, and wealth inequality is typically higher.

How to Use This Calculator

Enter comma-separated income values (e.g., individual or household incomes). The calculator sorts values, computes the Gini coefficient, builds the Lorenz curve, and calculates quintile shares. Click an example to load real-world distributions from the US, Sweden, South Africa, Japan, or theoretical extremes.

Results include the Gini coefficient, 90th/10th percentile ratio, top 20% income share, and mean income. Four charts visualize the Lorenz curve, country comparison, global trend, and quintile distribution.

Policy Implications

High Gini coefficients often correlate with lower social mobility, higher crime, and political instability. Policies that can reduce inequality include progressive income taxes, inheritance taxes, minimum wage increases, universal basic income, and investments in education and healthcare.

Nordic countries achieve low Gini through strong unions, collective bargaining, and generous welfare states. No single policy works everywhere — context matters. This calculator helps researchers and policymakers benchmark and track inequality over time.

Data Sources & Methodology

Country Gini values in this calculator are drawn from World Bank, CIA World Factbook, OECD, and United Nations databases. Methodology varies by source — some use disposable income (after taxes and transfers), others use market income. Comparability across countries requires caution.

The Gini formula used here is the standard discrete formula: G = |Σ(2i − n − 1) × x_i| / (n × Σx_i), where x_i are sorted income values. For small samples, bootstrap confidence intervals are recommended; this calculator provides point estimates suitable for illustrative and educational use.

Did You Know?

Gini Coefficient by Country (Approximate)