This doctoral dissertation, submitted to the University of Mannheim, was written during my employment as a research fellow at the Zentrum fiir Europaische Wirtschaftsforschung (ZEW - Centre for European Economic Research) in Mann­ heim. My work profited very much from the fruitful environment provided by the ZEW and particularly by the Department of Labour Markets, Human Resources and Social Policy. I am very grateful to my advisor, Professor Wolfgang Franz, for his support and inspiration. I am also indebted to Friedhelm Pfeiffer for encouraging me to work on the topicoftransition from unemployment to self-employment. Also, Part IIIof this study gained very much from the joint work with FriedheIm Pfeiffer. Fur­ thermore, I am much obliged to Professor JosefBniderl for evaluating this disser­ tation. I would like to thank the "Forderverein Wissenschaft und Praxis am Zentrum fiir Europaische Wirtschaftsforschung e.V." for financial support of part of this study. My work also benefited from the comments and the help of numerous people other than those mentioned above. Knowing that the list of acknowledgement is incomplete, I would like to thank Professor Francois Laisney and Matthias Almus for their valuable comments on the selection models, Professor William Greene for his helpful remarks on the bivariate probit model, Professor John Ham and an anonymous referee for their very valuable comments on preliminary work of this study, and Joachim Keller, Jens Kohlberger and Yibo Ren for providing excellent research assistance. Obviously, all remaining errors are my own responsibility.