zur Erlangung des Grades

When I began studying economics, I did not believe that I would ever be able to write a dissertation in this discipline. Too many mathematical formulas seemed to ask too much from my brain that intrinsically likes pictures and verbal stories. It needed several persons who continuously encouraged me to reach the point where I stand now. The first who believed in me was Oliver Fabel, who motivated me writing a dissertation after my diploma thesis. He also suggested the topic of this dissertation and acted as a supervisor. I am also very much indebted to Ulrich Kaiser for reviewing this dissertation as second supervisor and for supporting me with encouraging comments, in particular towards the end. In a completely un-complicated way, Uli also brought me into contact with the Centre for Economic and Business Research (CEBR) in Copenhagen, which provided me with access to Danish register data. This dissertation was written when I was research fellow at the Centre for European Economic Research (ZEW) in Mannheim. The ZEW offers an inspiring research environment where the doors are always open and the communication lines ar