"The Iron Law of Evaluation: “The expected value of any net impact assessment of any large scale social program is zero.”
The Iron Law arises from the experience that few impact assessments of large scale social programs have found that the programs in question had any net impact. The law also means that, based on the evaluation efforts of the last twenty years, the best a priori estimate of the net impact assessment of any program is zero, i.e., that the program will have no effect.
The Stainless Steel Law of Evaluation: “The better designed the impact assessment of a social program, the more likely is the resulting estimate of net impact to be zero.”
This law means that the more technically rigorous the net impact assessment, the more likely are its results to be zero—or not effect. Specifically, this law implies that estimating net impacts through randomized controlled experiments, the avowedly best approach to estimating net impacts, is more likely to show zero effects than other less rigorous approaches."