Impact Evaluation in International Development

Impact evaluations are studies that attempt to measure the causal impact of a project, program, or policy on an outcome of interest to governments and other interested parties. The purpose of this book is to provide a comprehensive set of skills that will enable the reader to conduct impact evaluations. The underlying assumption of this book is that impact evaluations are worth doing, even though they can be quite expensive and in some circumstances may not work. This raises the question of why they are worth doing, or more succinctly, why conduct evaluations? There are several answers to this question, which are explained in greater depth in subsequent chapters, but for now the following answers should be fairly compelling. Foremost, projects, programs, and policies should be evaluated to see whether they work. They can be expensive, and if they are ineffective, either they should be modified to be more effective, or they should be ended so that the resources required to implement them can be used for other purposes. In extreme cases, impact evaluations can demonstrate that projects, programs, and policies can be harmful, and thus should be modified or stopped to put an end to their harmful consequences. One example of a harmful impact is a policy in Peru requiring employers to provide permanent employees (those with 6 or 12 months of job experience) with additional benefits; to avoid providing these benefits, employers would lay off employees before they reached the threshold for permanent benefits. Impact evaluations provide valuable guidance on whether to adjust, expand, or end specific projects, programs, and policies.