"This book offers an accessible introduction to the topic of impact evaluation and its practice in development. It provides practical guidelines for designing and implementing impact evaluations, along with a nontechnical overview of impact evaluation methods .. The approach to impact evaluation in this book is largely intuitive. We have tried to minimize technical notation. The methods are drawn directly from applied research in the social sciences and share many commonalities with research methods used in the natural sciences. In this sense, impact evaluation brings the empirical research tools widely used in economics and other social sciences together with the operational and political economy realities of policy implementation and development practice. Our approach to impact evaluation is also pragmatic: we think that the most appropriate methods should be identified to fit the operational context, and not the other way around. This is best achieved at the outset of a program, through the design of prospective impact evaluations that are built into project implementation. We argue that gaining consensus among key stakeholders and identifying an evaluation design that fits the political believe that impact evaluations should be candid about their limitations and caveats. Finally, we strongly encourage policy makers and program managers to consider impact evaluations as part of a well-developed theory of change that clearly sets out the causal pathways by which a program works to produce outputs and influence final outcomes, and we encourage them to combine impact evaluations with monitoring and complementary evaluation approaches to gain a full picture of results." (Preface)