Income inequality is the uneven distribution of income across a population. Some people earn far more than others. The gap can be measured with the Gini coefficient, which ranges from 0 (perfect equality) to 1 (one person earns everything). Most countries fall between 0.25 and 0.60.

Inequality has risen in many developed countries since the 1980s. Technology, globalization, and changes in tax policy all play a role. Skilled workers have seen wages grow. Less-skilled workers have seen theirs stagnate. At the top, executives and financiers have pulled far ahead.

The consequences are debated. Some inequality reflects differences in effort, talent, and risk. Too much can undermine social cohesion, health outcomes, and economic mobility. Countries with lower inequality tend to have higher mobility. The relationship is not simple, but it is hard to ignore.

How it is measured

• Gini coefficient
• Top 10 percent income share
• Poverty rates
• Intergenerational mobility
• Wage ratios