Goodhart's Law: When a measure becomes a target, it ceases to be a good measure

And FYI the US handily and clearly won the Vietnam war; the South Vietnamese insurgency was defeated and the North Korean Army was obliterated.

Due to political pressure at home, the US withdrew after the war, and a short while later the North Vietnamese were able to rebuild their army and waltz in and topple the fragile S. Vietnamese government. The Communists then murdered 10's of thousands of people in the streets and imprisoned 100's of thousands and of course enforced totalitarian rule which kept millions in fear and poverty.

Were the Americans to have simply left a contingent of soldiers in the South, thereby keeping the legitimate threat of violence, it's unlikely the South would have fallen and might very well look like S. Korea today.

To your point, 'body count' is not a very good number to use when you're fighting an insurgency where there are a lot of irregular forces who can come in and out of fighting, or where soldiers can be replenished (i.e. North Vietnam can recruit willy nilly on their turf).

But it's still a valid measure and though you don't hear about it these days (for PR reasons) you can absolutely be assured that all NATO forces meticulously con't how many enemy forces are destroyed, and that it is a 'target' on many missions.

The gaming was done on the accounting side (revenue recognition) of course.

In fact, I think to argue against optimization, you’d basically have to boil it down to existing philosophical arguments against utilitarianism.

Either way, I’m skeptical if this conclusion is very connected to Goodhart’s Law, because it assumes some type of normative axiom that would have to precede your interpretation of Goodhart’s Law.

My main interest was to pointout that it creates a sort of impossibility theorem situation if you accept Goodhart’s Law (I don’t personally accept it as a general rule, only something that applies to some types of measures and not others).

The impossibility criteria would be something like:

- If one finds a good measure, one should optimize it.

- If a measure is an optimization target, it is not a good measure.

- For a given entity, there exists a set of variables governing how well that entity can meet a goal (e.g. measures can possibly contain relevant information).

Basically you could only choose 2.

- If you pick the first two, it means there are no general variables governing the outcone you want; they are constantly changing and fundamentally unpredictable, so you might get away with optimizing something briefly, but its informativeness immediately disappears. This type of thinking is common in efficient market theory, for example, and could be connected to a fundamental belief about non-determinism or non-stationarity.

- If you choose the first and third, it seems like standard utilitarianism.

- If you choose the latter two, it seems like fatalism or religion — there are quantities that govern achieving desired outcomes, but they cannot be treated as objective optimization criteria and can only be analyzed subjectively or fatalistically.