On the decomposition by sources of the Zenga 1984 point and synthetic inequality indexes

In this work we provide a decomposition by sources of the inequality index ζ defined by Zenga (Giornale degli Economisti e Annali di economia 43(5–6):301–326, 1984). The source contributions are obtained with the method proposed in Zenga et al. (Stat Appl X(1):3–31, 2012) and Zenga (Stat Appl XI(2):133–161, 2013), that allows to compare different inequality measures. This method is based on the decomposition of inequality curves. To apply this decomposition to the index ζ and its inequality curve, we adapt the method to the “cograduation” table. Moreover, we consider the case of linear transformation of sources and analyse the corresponding results.