Goodhart's Law

When a measure becomes a target, it ceases to be a good measure.

Goodhart’s law is a famous adage named after the British economist Charles Goodhart, which goes: “When a measure becomes a target, it ceases to be a good measure.”

There is a famous story involving some cobras and government in India. In British India, the government was concerned about the number of venomous cobras in Delhi. They came up with the idea to offer a bounty for every dead cobra that people brought to them.

Initially, things went well. People started bringing in slaughtered snakes. However, over time, people started breeding cobras so that they could kill them, and redeem the dead snakes for money.

The measure of "No. of dead snakes" became the target. This is a fairly common scenario in a business or life where choosing the wrong metric leads to people chasing the wrong target.

So next time you choose a metric as a target, take some time to reflect if it is truly aligned with your intentions.

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