This book provides an empirical and institutional analysis of ?scal federalism in OECD countries, focusing on the impact of economic and political integ- tion on the degree of public sector decentralisation. This work has been made possible through the ?nancial support of the German Research Foundation (DFG) within the Priority Programme "Institutional Design of Federal S- tems:TheoryandEmpiricalEvidence"andthroughdi?erentresearchprojects carried out at the Centre for European Economic Research (ZEW). First of all, I am very grateful to my supervisor Prof. Dr. Robert Sch- ger for ?nding interest in this topic and for giving me considerable freedom to write my doctoral thesis. I would like to thank him and Prof. Dr. Thiess B¨ uttner,whokindlyacceptedtobemysecondsupervisor,fortheircontinuous support throughout this work. Additionally, I am indebted to the Centre for European Economic Research (ZEW) and to Prof. Dr. Dr. h. c. mult. Wo- gang Franz for the excellent working and research conditions. I would also like to express my gratitude to all my colleagues from the ZEW Department of Corporate Taxation and Public Finance for the pleasant working envir- mentandmanyhelpfuldiscussions. Thanksarealsoduetoseveralanonymous referees and to participants in international conferences who with their cr- ical comments helped to improve the papers written during this time. I am also grateful to the student assistants, and particularly to Lena Lindlar, who provided able help in collecting and processing data and literature.