What Is the Gini Coefficient? Measuring Inequality

The Gini coefficient is a statistical measure of inequality within a population — most commonly applied to income or wealth distribution within a country. It ranges from 0 (perfect equality, where everyone has the same income) to 1 (perfect inequality, where one person has all the income). Most developed countries have Gini coefficients between 0.25 and 0.45: Scandinavian countries cluster around 0.25-0.28, the US sits at approximately 0.39-0.41, and some developing nations exceed 0.50.

How the Gini Coefficient Works

The Gini is derived from the Lorenz curve — a graph plotting the cumulative percentage of total income received by the bottom x% of the population. In a perfectly equal society, the Lorenz curve is a 45-degree line (the bottom 20% earns 20% of income, the bottom 50% earns 50%, and so on). In reality, the Lorenz curve bows below this line — the bottom 20% might earn only 4% of total income. The Gini coefficient measures the area between the actual Lorenz curve and the perfect equality line.

A higher Gini means more inequality — a wider gap between the richest and poorest members of society. A lower Gini means more equality — income is distributed more evenly across the population. Changes in the Gini over time reveal whether inequality is increasing or decreasing.

Why Inequality Matters for Markets

Rising inequality affects consumer spending patterns. When income concentrates at the top, aggregate demand can weaken because high-income households save a larger share of their income than lower-income households. This "savings glut" can reduce economic growth, lower interest rates, and shift corporate revenue toward luxury goods and financial services while weakening demand for mass-market consumer products.

The US Gini coefficient has risen steadily since the 1970s — from roughly 0.35 to 0.41. This increase coincides with the growth of technology companies (which concentrate wealth among founders and early employees), the decline of manufacturing (which previously provided middle-class wages), and policy changes (lower top marginal tax rates, weaker labor protections). The trend toward higher inequality has benefited luxury brands, financial services, and technology stocks while creating headwinds for companies dependent on broad-based consumer spending.

Inequality also creates political risk. High Gini coefficients are associated with populist political movements, which often advocate for policies that affect businesses: higher corporate taxes, stricter regulation, expanded social programs, and trade protectionism. The political response to inequality can shift the business environment in ways that affect corporate earnings and stock valuations.

Inequality and Quality Investing

Quality investors should be aware of inequality trends because they shape consumer markets, political environments, and economic growth trajectories. Companies whose customer base spans the income spectrum are more resilient to inequality-driven demand shifts than those dependent on a single income cohort.

More practically, wide-moat businesses with essential products and pricing power are positioned to serve customers across the income distribution. Whether inequality is rising or falling, people need healthcare, utilities, financial services, technology, and consumer staples. Quality businesses in these sectors earn returns driven by competitive advantage rather than by the income distribution of their customer base.