This book will appeal to scholars and policymakers who deal with and/or are conducting research on the factors of economic growth. At present, there is no unified growth model that is feasible for every investigation. As such, this volume offers key insights into the factors that are most relevant in explaining growth variation at country, regional and metropolitan levels. In order to acquaint the reader with the concepts related to the subject, two theoretical chapters detail the schools of thought and the models that were formulated in the past. Three empirical chapters then present an up-to-date and a multi-level investigation, using the most comprehensive models, for the European Union. The results of this book are policy-oriented and will serve to help close the gaps between EU countries and regions.