The measurement of income polarization by ethnic groups: The case of Israel population

Income polarization is a relatively new concept introduced in the literature of the measurement of income inequality. It has essential properties that may be used to measure relative deprivation and it adds another dimension to the measurement of income inequality concerned mainly with the middle income class (Esteban and Ray, 1994). No study, however, seems to have tried to decompose by population subgroups any of the polarization indices that have appeared in the literature. This study introduces a methodology that decomposes the polarization index recently suggested by Deutsch et al. (2007) by population subgroups. This polarization index is related to the Gini index and its components so that previous results on the decomposition of the Gini index may be applied. Two main cases are examined, that of nonoverlapping groups and overlapping groups. The paper also includes an empirical analysis based on Israeli data for the period 1990-2004, which covers the case of nonoverlapping (income) groups as well as that of overlapping groups, the latter being either Jews of Western and Eastern origin or Jews and Non-Jews. The empirical analysis shows a decrease in polarization over the period 1990-2002 and an increase in polarization during the years 2002-2004. Using the Shapley methodology we analyze the contribution of the different factors to the trend in polarization observed over time.