The Gini coefficient (G) is an index for measuring inequality. This entry reviews the use of the G since its appearance in the literature in 1914. It discusses how the Italian statistician Corrado Gini developed it. The entry highlights methodological aspects to explain the various formulas that can be used to calculate the G value and to show the links with the Lorenz curve and the mean difference. It also discusses how some scholars have come to the same results using different formulas of G, depending on the investigated subject. An application to real data is also provided in order to make the use of G simple and immediate. Finally, the extreme topicality of the Gini index is underlined by showing how it is currently used in fields other than economics - such as in archaeology, hydrology, insurance, biomedicine, geosciences, and to evaluate scientific productivity of universities and departments.

More than a century ago, Corrado Gini proposed his well-known concentration index for measuring the degree of inequality in the distribution of income and wealth. His index is still extremely relevant and widely used in several fields of research and application. In this paper, we focus on the inferential properties of the Gini index, and discuss the main directions of analysis proposed in the literature. The aim of the paper is to provide a comprehensive review of the main developments on the inferential aspects of the Gini concentration ratio. We feel that this work can provide a valuable contribution to those scholars who are approaching the large amount of literature on the inferential properties of the Gini index.