Measuring Inequality of Opportunity through Between-Group Inequality Components

Opportunity egalitarians support rich-to-poor redistribution whenever this allows for the compensation of income disparities due to non-responsible choices (circum- stances). In this paper we investigate the measurement of opportunity inequality within Roemer's (1993) pragmatic theory where equally subgroup ranked individuals are assumed to be equally responsible. Given entropy-based, deprivation-based and welfaristic inequality decomposition procedures, we show that the between-group Gini index - obtained from the two-components decomposition (Dagum 1997) - is the only between-group inequality index satisfying the Pigou-Dalton principle of transfer as reformulated for opportunity egalitarianism.