Two extensions of the univariate Gini index are considered: R D , based on expected distance between two independent vectors from the same distribution with finite mean + # R d ; and R V , related to the expected volume of the simplex formed from d+1 independent such vectors. A new characterization of R D as proportional to a univariate Gini index for a particular linear combination of attributes relates it to the Lorenz zonoid. The Lorenz zonoid was suggested as a multivariate generalization of the Lorenz curve. R V is, up to scaling, the volume of the Lorenz zonoid plus a unit cube of full dimension. When d=1, both R D and R V equal twice the area between the usual Lorenz curve and the line of zero disparity. When d>1, they are different, but inherit properties of the univariate Gini index and are related via the Lorenz zonoid: R D is proportional to the average of the areas of some two-dimensioned projections of the lift zonoid, while R V is the average of the volumes of projections of the Lorenz zonoid over all coordinate subspaces.
Academic Press