Goodhart's law: chasing marks, missing the chapter
Goodhart's law says a number stops telling the truth once people are rewarded for it, tried here on a Class 8 boy who scores 95 in science and cannot explain the chapter.
- work
- autopilot
- hermes
The report card is on the fridge. Science: 95. Sunita buys mithai and Kabir's father sends the photo to the family group. Two days later Kabir's mama is visiting from Jaipur, picks up the science book and asks one plain question from the same chapter: why does a spoon in hot dal get warm at the handle? Kabir, who is in Class 8, looks at the floor.
Nobody did anything wrong here. Kabir is not weak, because he scored 95. His teacher did not teach badly, because the whole class did well. Something else is going on.
What the model says
The idea is called Goodhart's law, after the economist Charles Goodhart. In plain words: a number that used to tell you something true stops telling you the truth once people are rewarded for the number itself. The number was only a stand-in for something you cared about. Once the stand-in is what everyone asks about, people learn to produce the stand-in.
The example, step by step
Marks were meant to show that a child understands the chapter. For a while they do. Then every conversation at home starts with "how many marks?" and the mithai, the praise and the family group photo all follow the number.
Kabir is smart, so he notices what is rewarded. He learns which questions come back every year. He memorises the answers to them and practises the sums in the format the paper uses. All of that is sensible. It raises the number. But it does not touch the thing the number was standing for, so the mark climbs while the understanding stays where it was.
The same shape shows up in a call centre that rewards short calls. Agents end calls quickly, and the number looks wonderful. Customers call back with the same problem. The number rose and the thing it was meant to measure did not.
Where it stops
The answer is not to throw the number away. Marks and call times still tell you something. The trap is to read the number alone, or to blame whoever is chasing it. A child or an agent who chases the number is doing what the system asked.
What helps is a second check placed next to the number, aimed at exactly what the number can miss. For marks, that is a question that cannot be answered by remembering the answer key.
One thing to try today
Tonight, when you ask about marks or any other number, ask one more thing beside it: "Explain this to me as if I have never seen it." Pick one topic, give it five minutes, and listen without correcting. If the explanation is shaky, say only "let us look at it together on Sunday" and write the topic on the fridge.
It may feel slow the first time, and the child may feel tested. Keep your voice light.
The number is going up. Is the thing you wanted to measure going up too?
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