Chapter 20 of the Ministry for the Future begins with a description of the Gini coefficient.

From Wikipedia:

In economics, the Gini coefficient, also known as the Gini index or Gini ratio, is a measure of statistical dispersion intended to represent the income inequality or the wealth inequality or the consumption inequality within a nation or a social group. It was developed by statistician and sociologist Corrado Gini.

Gini coefficient - Wikipedia

World map of income inequality Gini coefficients by country (as %). Based on World Bank data ranging from 1992 to 2020. A different map showing Gini coefficients but then for wealth within countries for 2019