Working Paper

The Politics and Practice of Social Experiments

Seeds of a Revolution


Between 1970 and the early 2000s, there was a revolution in support for the use of randomized experiments to evaluate social programs. Focusing on the welfare reform studies that helped to speed that transformation in the United States, this paper describes the major challenges to randomized controlled trials, how they emerged and were overcome, and how initial conclusions about conditions necessary to success — strong financial incentives, tight operational control, and small scale — proved to be wrong.