Two Types of Inequality: Inequality Between Persons and Inequality Between Subgroups

Any opinions expressed here are those of the author(s) and not those of the institute. Research disseminated by IZA may include views on policy, but the institute itself takes no institutional policy positions. The Institute for the Study of Labor (IZA) in Bonn is a local and virtual international research center and a place of communication between science, politics and business. IZA is an independent nonprofit company supported by Deutsche Post World Net. The center is associated with the University of Bonn and offers a stimulating research environment through its research networks, research support, and visitors and doctoral programs. IZA engages in (i) original and internationally competitive research in all fields of labor economics, (ii) development of policy concepts, and (iii) dissemination of research results and concepts to the interested public. IZA Discussion Papers often represent preliminary work and are circulated to encourage discussion. Citation of such a paper should account for its provisional character. A revised version may be available directly from the author. ABSTRACT Two Types of Inequality: Inequality Between Persons and Inequality Between Subgroups * Social scientists study two kinds of inequality: inequality between persons (as in income inequality) and inequality between subgroups (as in racial inequality). This paper analyzes the mathematical connections between the two kinds of inequality. The paper proceeds by exploring a set of two-parameter continuous probability distributions widely used in economic and sociological applications. We define a general inequality parameter, which governs all measures of personal inequality (such as the Gini coefficient), and we link this parameter to the gap (difference or ratio) between the means of subdistributions. In this way we establish that, at least in the two-parameter distributions analyzed here, and for the case of two nonoverlapping subgroups, as personal inequality increases, so does inequality between subgroups. This general inequality parameter also governs Lorenz dominance. Further, we explore the connection between subgroup inequality (in particular, the ratio of the bottom subgroup mean to the top subgroup mean) and decomposition of personal inequality into between-subgroup and within-subgroup components, focusing on an important decomposable measure, Theil's MLD, and its operation in the Pareto case. This allows us to establish that all the quantities in the decomposition are monotonic functions of the general inequality parameter. Thus, the general inequality parameter captures the " deep structure " of inequality. We also introduce a whole-distribution graphical tool for assessing personal and subgroup inequality. Substantively, this work …