Defence date: 14 June 2018Examining Board : Prof. Árpád Ábrahám, EUI, Supervisor ; Prof. Dominik Sachs, EUI and University of Munich ; Prof. Nicola Pavoni, Bocconi University ; Prof. Ali Shourideh, Carnegie Mellon UniversityThe three chapters of this thesis provide a theoretical and quantitative analysis of three elements of the tax-transfer system which recently received increased attention in both the academic and the public policy debate in the United States and Europe. In the first chapter, I show theoretically that optimal taxes on business owners are not entirely characterized by the usual, well established, equity-eficiency trade-off but that additional \trickle down" effects reduce optimal tax rates. As taxes on business income redu...