Abstract
The purpose of this study is to analyze the relationship between parameters of subpopulation and the Gini coefficient of whole society. For this purpose, we introduce a parametric decomposition of the Gini coefficient under the condition that each income in a subpopulation is subject to the lognormal distribution. By this condition, the overall Gini coefficient can be expressed as a function of the parameters of subpopulation's distribution, that is μi and σi. Applications of the parametric decomposition are made to the household income distribution that consists of age-subpopulations in Japan.
