We develop and estimate a model of jointly optimal income taxes for different types of income. Compared to standard optimal tax formulas, optimal schedular income tax rates additionally depend on cross-elasticities between tax bases capturing fiscal externalities. We discuss two applications:...

Does party competition affect political activism? This paper studies the decision of party supporters to join political campaigns. We present a framework that incorporates supporters' instrumental and expressive motives and illustrates that party competition can either increase or decrease...

How does a citizen's decision to participate in political activism depend on the participation of others? We conduct a nation-wide natural field experiment in collaboration with a major European party during a recent national election. In a seemingly unrelated survey, we randomly provide...

We study participation in right-wing rallies and counterrallies in Germany to examine strategic interactions in political movements. In the leadup to two right-wing rallies, we exogenously shift potential participants' beliefs about the turnout at the right-wing rally and left-wing counterrally,...