What it is
Goodhart’s law, in Marilyn Strathern’s popular phrasing: “When a measure becomes a target, it ceases to be a good measure.” The economist Charles Goodhart made the original point about monetary policy in 1975.
Once people are rewarded for a number, they find ways to move the number that don’t move the thing it was supposed to show. Reward tickets closed, and work gets split into tiny tickets. Reward clicks, and you get outrage.
How it shows up for me
Every metric I set for a team will get gamed toward the number instead of the goal, and not because people are bad. They’re just doing what I rewarded. So I try to change metrics often, and keep asking what the number was supposed to tell me.