Social experiments use random assignment to measure the market or fiscal outcomes of policy interventions. Since the 1960s, they have become the major method for evaluating proposed changes in social programs. To judge the social gains of these experiments, policymakers, funders of experiments, the public, and those who conduct social experiments need realistic standards and expectations for judging.Social Experimentation and Public Policymaking advances that effort with a history of social experimentation and a theoretical framework for study of its techniques. The authors analyze five of the most prominent social experiments ever conducted, to explore their origins, the use of the resulting findings, and factors that influenced the use of the findings. The result is a comprehensive examination of the effectiveness of social experimentation and important insights into how this powerful tool can be used to improve public policy.