- noun (written as Gini coefficient)a way of measuring inequality in incomes within a society developed by Corrado Gini (1884–1965), an Italian statistician. It is the ratio between the 45 ¦ line and a Lorenz curve below the 45 ¦ line.
The Gini coefficient was invented by the Italian statistician Corrado Gini (1884-1965) as a measure of income inequality, though it can be (and has been) used to measure, say, the distribution of health or of health care resource consumption. The Gini coefficient is a number between 0 and 1, where 0 corresponds to perfect equality (everyone has the same income, health care, etc.) and 1 is perfect inequality (one person has all the income, health care, etc.). While the Gini coefficient is mostly used to measure income inequality, it can be used to measure wealth inequality as well.
The Gini coefficient is related to the areas in a Lorenz diagram. Let the area between the line of perfect equality and Lorenz curve be A, and the area underneath the Lorenz curve be B, then the Gini coefficient is A/(A + B).