One of the major problems with aid is that we cannot be sure of its impact. Does aid work or not? This book examines the economic impact of aid. But not in the sense that it questions the relevance of this objective, or tries to measure whether aid works or not. The focus of this book is on the evaluation process itself. What determines international aid agencies search for knowledge about the economic impact of their operations? Can aid evaluation be improved in order to increase the effectiveness of aid?