Gini coefficient is an index to judge the fairness of income distribution according to the Lorenz curve defined by German economist albert hirschman in 1943. It is an important analytical index used to comprehensively examine the income distribution differences of residents in various countries in the world.

Its specific meaning refers to the proportion of all residents' income used for uneven distribution. The maximum value of Gini coefficient is "1" and the minimum value is "0". The former means that the income distribution among residents is absolutely unbalanced, that is, 100% of the income is occupied by the owner of a unit; The latter means that the income distribution among residents is absolutely average, that is, the income between people is completely equal, without any difference. But these two situations are only absolute forms in theory, and generally do not appear in real life. So the actual value of Gini coefficient can only be between 0 and 1. The smaller the Gini coefficient, the more average the income distribution, and the larger the Gini coefficient, the more uneven the income distribution. 0.4 is usually regarded as a warning line for the gap between the rich and the poor in the world. If it is greater than this value, social unrest will easily occur.