Income tax progressivity is studied with Generalized Entropy measures of inequality. Luxembourg Income Study data sets for nine countries are used for international comparison and analysis. progressivity indices are generated by using the Generalized Entropy family as well as Atkinson measures. We further our understanding by examining pre-tax and post-tax measures of inequality based respectively on gross and disposable household incomes. The decomposition property is shown to be desirable for enhancing our knowledge of income inequality and the redistributive effect of income taxes. Thus decomposition based on family size and number of earners is conducted. We learn that countries vary in their emphasis regarding redistributive effects of income taxes.