1. The Stainless Steel Law: The better designed the outcome evaluation, the less effective the intervention seems.
2. The Iron Law: The expected value of any impact assessment of any large scale social programme is zero.
3. The Brass Law: The more social programs are designed to change individuals, the more likely the net impact of the program will be zero.
4. The Zinc Law of Evaluation: Only those programs that are likely to fail are evaluated.
Peter Rossi: The iron law of evaluation and other metallic rules. Research in Social Problems and Public Policy. 4:3, 1987.