Goodhart’s Law is the quiet engine behind most measurement failures: once you pay people against a number, they optimize the number, not the thing it was supposed to represent. Attach money to impressions and you will get impressions, whether or not anyone saw anything.

The corollary matters just as much and gets said less often: just because there is no measure does not mean the thing does not exist. We treat the unmeasured as the unreal. But a fraud you cannot yet count is still happening; you simply lack the evidence to price it.

The unmeasured is not the nonexistent. It is only the unaccounted-for.

Hold both at once and you get a working stance toward metrics: distrust the number you are paid to move, and refuse to assume the absence of a number is good news. Most of the interesting risk lives in the gap between the two.