Well for one, it's hard not to conflate when you're expecting me to know what you mean as opposed to what you say.
Second off, you don't think it's possible to hide costs, exaggerate revenue, ignore risks, and/or optimize short term revenue in favor of long term? If you think something isn't hackable you just aren't looking hard enough
What, in your opinion, is any for profit business ultimately trying to (legally) maximize? I'd say it is NPV. That can mean taking risks, optimizing short term revenue in favor of long term (and vice versa).
I'm not an expert in this space so I'm not comfortable giving precise examples. If you want a naive "I've read Wikipedia and a few articles via Google searching" I can give you that.
But I'm suspicious of a claim that it can't be hacked. I've done a lot of experimental physics and I can tell you that you can hack as simple and obvious of a metric as measuring something with a ruler. This being because it's still a proxy. Your ruler is still an approximation of a meter and is you look at all the rulers, calipers, tape measures, etc you have, you will find that they are not exactly identical, though likely fairly close. But people happily round or are very willing to overlook errors/mistakes when the result makes sense or is nice. That's a pretty trivial system, and it's still hacked.
With more abstract things it's far easier to hack, specifically by not digging deep enough. When your metrics are the aggregation of other metrics (as is the case in your example) you have to look at every single metric and understand how it proxies what you're really after. If we're keeping with economics, GSP might be a great example. It is often used to say how "rich" a country is, but that means very little in of itself. It's generally true that it's easier to increase this number when you have many wealthy companies or individuals, but from this alone you shouldn't be about to statements two countries of equal size where all the wealth is held by a single person or where wealth is equally distributed among all people.
The point is that there's always baked in priors. Baked in assumptions. If you want to find how to hack a metric then hunt down all the assumptions (this will not be in a list you can look up unfortunately) and find where those assumptions break. A very famous math example is with the Banach-Taraki paradox. All required assumptions (including axiom of choice) appear straight forward and obvious. But the things is, as long as you have an axiomatic system (you do), somewhere those assumptions break down. Finding them isn't always easy, but hey, give it scale and Goodhart's will do it's magic
https://en.wikipedia.org/wiki/Net_present_value#Disadvantage...