Preface and acknowledgements

Natural experiments have become ubiquitous in the social sciences. From standard natural experiments to regression-discontinuity and instrumental-variables designs, our leading research articles and books more and more frequently reference this label. For professional researchers and students alike, natural experiments are often recommended as a tool for strengthening causal claims.

Surprisingly, we lack a comprehensive guide to this type of research design. Finding a useful and viable natural experiment is as much an art as a science. Thus, an extensive survey of examples – grouped and discussed to highlight how and why they provide the leverage they do – may help scholars to use natural experiments effectively in their substantive research. Just as importantly, awareness of the obstacles to successful natural experiments may help scholars maximize their promise while avoiding their pitfalls. There are significant challenges involved in the analysis and interpretation of natural-experimental data. Moreover, the growing popularity of natural experiments can lead to conceptual stretching, as the label is applied to studies that do not very credibly bear the hallmarks of this research design. Discussion of both the strengths and limitations of natural experiments may help readers to evaluate and bolster the success of specific applications. I therefore hope that this book will provide a resource for scholars and students who want to conduct or critically consume work of this type.