The World Bank recently introduced a new key indicator to guide its work: the number of countries with high inequality, defined as a Gini index above 40. The new indicator was introduced as part of the new World Bank vision of ending poverty on a livable planet. This paper reviews why reducing inequality matters for ending poverty on a livable planet, summarizes the advantages and disadvantages of using the Gini index to track inequality, outlines challenges in measuring inequality, and discusses what a Gini threshold of 40 implies. Using the most recent data for every country, 52 countries of a total of 169 countries are classified as high inequality countries, which represents a decline from 74 countries at the beginning of the millennium.