Revision with unchanged content. The question of regulatory quality draws increasing attention in literature and practice. One instrument to monitor high regulatory quality is impact assessment. This book traces the major developments of impact assessment in the European Union. It consists of two parts. The first part delivers the theoretical background. It looks at the political justification and economic reasoning and gives an introduction into the actual practice and quality of impact assessment in the European Union. The second part includes a case study. Here, the author analyzes how impact assessment is performed in practice. In addition, insight is given to the economic modeling behind REACH. The book addresses all readers interested in sustainability and good governance of the European Union: researchers, students, consultants and others.