Abstract
This paper presents, under a general condition, the formula which expresses the Gini coefficient as a function of relative sizes of subgroups, and shows that, in two subgroups case, the shape of the graph of Gini coefficient as a function of relative size is classified into three types according to the position of inter-subgroup Gini coefficient between two intra-subgroup Gini coefficients. The general condition which enables this analysis is that each intra-subgroup distribution is kept unchanged when relative sizes are changing.
