Concept
Goodhart's Law
Goodhart's law states that when a measure becomes a target, it ceases to be a good measure, because people begin to optimise the number instead of the thing the number was meant to represent.
The principle is named after the British economist Charles Goodhart, who observed it in monetary policy in 1975; the popular one-sentence form was written by the anthropologist Marilyn Strathern. It applies far beyond economics. James Clear uses it in Atomic Habits to warn habit-trackers: the step count, the pages read, the streak length all begin as honest signals of a purpose and end, if you are not careful, as the purpose itself, chased in ways that no longer serve it. What people get wrong is concluding that measurement is the problem. Measurement is fine; it is the moment the number replaces the reason that the distortion begins, and the fix is to keep asking what the number was for.
A real-life example
A team is rewarded for closing support tickets quickly. Within a month, tickets are closed with 'please reopen if needed' and satisfaction falls while the closing time looks superb. The number is being hit; the purpose, helped customers, has left the room.
How to use it
- 1Next to every number you track, write the one-line purpose it stands for.
- 2Review the number and the purpose together, and change the measure the moment they diverge.
- 3Pair a quantity with a quality: not only how many, but how well, or how it felt.