Campbell's Law

Campbell's Law was articulated by sociologist Donald T. Campbell in 1976: the more any quantitative social indicator is used for social decision-making, the more subject it will be to corruption pressures and the more apt it will be to distort and corrupt the social processes it is intended to monitor.

Campbell's Law is the social science formulation of the same structural observation captured by Goodhart's Law in economics. The two laws converge on the same mechanism — proxy measures degrade under optimization pressure — but Campbell emphasizes the corrupting effect on the social processes being measured, not merely on the accuracy of the metric. When standardized test scores become high-stakes targets, teaching shifts toward test preparation; the test corrupts the educational process it was designed to evaluate, not merely its own validity.

The corruption Campbell describes is not limited to deliberate gaming. The distortion occurs even when all participants act in good faith, because the incentive structures reshape which behaviors are rewarded and which are selected out. This is Goodhart dynamics operating at the level of institutional evolution — the institutions that survive are those adapted to the metric environment, regardless of whether they serve the original purpose.

Campbell's deeper insight, which the metric-corruption framing sometimes obscures: we do not have an alternative to quantitative social indicators for governing large-scale social systems. The question is not whether to use them but how to manage the inevitable corruption they introduce. No satisfactory answer has been found. The search continues in Mechanism Design, Robust Statistics, and AI Alignment.