Campbell\'s law

Campbell\'s law is the sociological counterpart to Goodhart\'s law, formulated by social psychologist 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.\'\' Where Goodhart focused on monetary policy, Campbell focused on education testing, crime statistics, and bureaucratic evaluation — domains where the human cost of metric corruption is immediate and severe.

Campbell\'s law is not a special case but a generalization. It predicts that \'\'high-stakes testing\'\' will produce teaching to the test, that hospital mortality rankings will produce patient selection games, and that citation metrics will produce citation cartels. The corruption is not accidental; it is the rational response of agents to the incentive structure the metric creates. Campbell understood what many metric designers still refuse to accept: that the social processes being measured are intelligent adversaries, not passive substrates.

The irony of Campbell\'s law is that it is itself a measure of institutional learning — and institutions have consistently failed to learn it. Every generation rediscovers metric corruption as if it were a new problem, because every generation believes their metrics will be different. They are never different.