Kontra has a useful reminder:
"When a measure becomes a target, it ceases to be a measure."
— Kontra (@counternotions) July 15, 2017
We see applications of this all the time. One famous example is the notion that we should use standardized tests to measure teacher/school effectiveness and base compensation/budgets appropriately. It’s one of those ideas that sounds good when you first hear it—who isn’t for rewarding more effective teachers, after all—but in reality those being measured soon learn how to game the system and we end up with “teaching to the test.”
We see it in our own industry every time some bean counter decides to evaluate programmer productivity by counting lines of code committed or some equally silly measure. Whatever the metric, programmers soon learn to maximize it even if the result is less and poorer quality work getting done.
The idea that making some measurement a target results in the measurement becoming useless is so common that it even has a name, Goodhart’s Law. It’s one of those things that everyone knows but always fail to take into consideration when starting out to measure some human activity with the aim of affecting policy in some way that matters to those being measured.