Just a side note that this usage isn't really the application Goodhart had in mind. Suppose you're running a central bank and you see a variable that can be use

Just a side note that this usage isn't really the application Goodhart had in mind. Suppose you're running a central bank and you see a variable that can be used to predict inflation. If you're doing your job as a central banker optimally, you'll prevent inflation whenever that variable moves, and then no matter what happens to the variable, due to central bank policy, inflation is always at the target plus some random quantity and the predictive power disappears. As "Goodhart's law" is used here, in contrast, the focus is on side effects of a policy. The goal in this situation is not to make the target useless, as it is if you're doing central bank policy correctly.