Goodhart’s Law is a mental model I am sharing to add to your cognitive toolkit. The ideas were first shared by Charles Goodhart, a leader in monetary policy, at a conference in Sydney, Australia, in 1975.
During a presentation, he said:
“Any observed statistical regularity will tend to collapse once pressure is placed upon it for control purposes.”
“When a measure becomes a target, it ceases to be a good measure.”
According to Peter Coy, it was Marilyn Strathern who coined this more accessible version.
It got me thinking about assessment, monitoring and evaluation in education. So many elements of our system(s) relate to this mental model and its contradiction. What springs to mind for you?
From the Peter Coy article, I also love the following example of Goodhart’s Law:
when Soviet planners ordered nail factories to increase the number of nails they produced, it’s said that managers reacted by producing millions of tiny, useless nails. When the planners wised up and switched to a weight criterion, the factories started producing giant, heavy, and equally useless nails. It’s hard to pin down the historical truth of these stories, but the point is clear.
Coy provides a range of other examples from modern life and explains that simply being aware of the pitfalls of measurement is a good step.
I know I will be using this mental model to think about assessment and review feedback.
get away from fixed, changeless rules that can be easily gamed. Also, measure what you actually want, not a rough proxy for it. Try using multiple criteria instead of a single standard. But the first step is simply to be aware of the problem. Putting a name and a focus on the pitfalls of measurement and reward is the lasting contribution of Charles Goodhart.