Pedro Arantesrose

Goodhart's Law

It stands that a measure ceases to be a good measure when it becomes a target.
Zettelkasten, June 22, 2021 (changes)


  • It stands that a measure ceases to be a good measure when it becomes a target.

  • Charles Goodhart advanced this idea in 1975.

  • When we pick a feature of the economy as an indicator of the economy, it ceases to function as that indicator because people start to game it.

    • The same happens to statistical variables.
  • It's a system mental model because it explains how a system works when a measure becomes the target.

  • Using multiples targets avoids Goodhart's Law because you must increase them all, not only one.

  • If you measure people on the number of nails made, you might get many tiny nails. If you measure the weight of nails made, you might get a few giant and heavy nails.

  • Educational systems that measure the students by grades incentivize them to memorize content for a test, then promptly forget it all.


  • How do you avoid Goodhart's Law?


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