https://en.wikipedia.org/wiki/Goodhart%27s_law
Goodhart’s law is an adage named after economist Charles Goodhart, which has been phrased by Marilyn Strathern as “When a measure becomes a target, it ceases to be a good measure.” One way in which this can occur is individuals trying to anticipate the effect of a policy and then taking actions that alter its outcome. His original formulation was: “Any observed statistical regularity will tend to collapse once pressure is placed upon it for control purposes.”
