“The Iron Law of Evaluation and Other Metallic Rules.”39 In it, Rossi made a startling claim. The Iron Law of the title stated, “The expected value of any net impact assessment of any large scale social program is zero.” That is, on average, large social programs show no impact. Rossi spent much of the paper considering this discouraging conclusion, and his analysis foretold the problems of packaged interventions. He explicitly noted three reasons why social programs so often fail when they go big.
