On Decomposition of the Gini Index of Equality

The purpose of this paper is to show that the Gini index of equality is: (i) subgroup decomposable throughout interpersonal comparisons; (ii) decomposable by income source; (iii) decomposable both by subgroup and income source; (iv) and decomposable in a multidimensional context permitting statistical inference on equality components. These results entail that decision makers must use the Gini index of equality decompositions since they imply necessarily the computation of the Gini index of inequality decompositions. The reverse is not true.