Goodhart's Law
The moment you measure something and start rewarding the number, the number stops telling you what it used to.
1975 (Goodhart's formulation), 1997 (Strathern's phrasing)14 min read
American social psychology and methodology
Donald T. Campbell
1916 – 1996
American social scientist who did foundational work on research design, validity and evaluation. His writing on planned social change gave the corruption of social indicators its sharpest independent statement, now known as Campbell's Law.