Notes
-
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.
Questions
- How do you avoid Goodhart's Law?