Income tax progressivity is studied using Generalized Entropy measures of inequality. Luxembourg Income Study data sets for ten countries are used for international comparative purposes and analysis. Progressivity indices are generated using the Generalized Entropy family as well as Atkinson measures. This is to test the robustness of our observation of tax progressivity in each country. We further our understanding by looking at pre-tax and post-tax measures of inequality based on gross household income and disposable household income, respectively. The decomposition property is shown to be desirable in order to enhance our view of true inequality and the implication of taxes. Thus decomposition based on quintile, family sizes, and number of earners is conducted. This has allowed an interpretation of results that could be attributed to any of the above characteristics and components which are free of such group characteristics.