Goodhart’s Law and Emotions
When a measure becomes a target, it ceases to be a good measure. — Marilyn Strathern Goodhart’s law is an important principle about using a measure to drive action. Imagine a city that is trying to reduce crime. The mayor tells the police chief to “Get the crime rate down!”. But what is the crime rate? It is a statistical metric of crimes per capita. The police measure the crime rate by making reports about crimes. Knowing that his job is on the line, the police chief tells his officers to go easy on crime reports. “Don’t file a report unless it is serious.” he tells them. So, the crime rate (as measured) goes down, while the actual number of crimes goes up, because criminals learn that they are less likely to be punished, and citizens learn that there is no point calling the police over minor crimes. Eventually, word gets back to the mayor, and he fires the police chief. He hires a new police chief, and gives him a different instruction. “I want to see m