What does Godhart’s law mean?

Question

It goes “When a measure becomes a target, it ceases to be a good measure.” How does that work in practice?

In: Other

Answer 1

Nail factory rewards employee for number of nails made = employee makes a lot of uselessly small nails

Nail factory rewards employee for total weight of nails made = employee makes very heavy, uselessly large nails.

“Measure becomes target” basically means “gaming the system”