In economics, what coefficient summarizes income or wealth inequality on a scale from 0 to 1?

In economics, the Gini coefficient summarizes income or wealth inequality on a scale from 0 to 1.

Italian statistician Corrado Gini introduced the measure in 1912. A value of 0 represents perfect equality, while a value of 1 represents maximum inequality in the standard interpretation, where one person or household has all the income or wealth and everyone else has none. Some publications multiply the result by 100 and report a Gini index instead.

The coefficient is derived from the Lorenz curve, which compares the cumulative share of income or wealth received by cumulative population groups. The farther the Lorenz curve lies from the equality line, the higher the Gini value.

The measure does not explain why inequality exists or identify the living standards of the poorest people. Two countries can have the same coefficient while having very different income distributions, taxes, and poverty rates.