Goodhart's Law has a precise formulation but the pathology it describes is ancient: the moment a measure becomes a target, it ceases to be a good measure. Every auditor learns this, every program evaluator learns this, and then predictably a new round of metrics gets designed, gamed, and discarded. When the French colonial government in Indochina offered a bounty per rat tail, entrepreneurs started farming rats to collect the bounty, and the rat population grew. When NHS targets measured how ...

Goodhart's Law has a precise formulation but the pathology it describes is ancient: the moment a measure becomes a target, it ceases to be a good measure. Every auditor learns this, every program evaluator learns this, and then predictably a new round of metrics gets designed, gamed, and discarded. When the French colonial government in Indochina offered a bounty per rat tail, entrepreneurs started farming rats to collect the bounty, and the rat population grew. When NHS targets measured how ...