“…This question has interested researchers and policymakers alike in the wake of a decline over several decades in income tax progressivity around the Western world. Several studies have examined the issue, looking at either cross-country evidence or within-country variation over the income distribution (see, e.g., Feenberg and Poterba, 1993;Slemrod, 1996;Slemrod and Bakija, 2000;Brewer, Saez and Shephard, 2010;Bach, Corneo and Steiner, 2013;Förster, Llena-Nozal and Nafilyan, 2014;Piketty, Saez and Stantcheva, 2014;Duncan and Sabirianova Peter, 2016;Frey andSchaltegger, 2016 andSaez, 2017), but the complex interdependence between income taxation and income inequality poses powerful hurdles to identify this relationship and it is fair to say that consensus has not been reach over how it looks.…”