Goodhart’s Law: How to Create the Behavior Change You Actually Want

In the 1940s, paleontologist Gustav Heinrich Ralph von Koenigswald went on an expedition to the island of Java in Indonesia.

He wanted to find as many hominid bones as possible, so he decided to enlist the help of the locals.

As an incentive, he promised anyone who helped him ten cents for every hominid bone they brought him.

It seemed like a reasonable arrangement.

Until von Koenigswald, to his horror, discovered that the locals enthusiastically had been smashing big bone pieces into smaller ones to maximize their income1.

Goodhart’s Law

The story of von Koenigswald’s Java expedition provides a striking example of Goodhart’s Law2:

When a measure becomes a target, it ceases to be a good measure.

It’s named after the economist Charles Goodhart, who described the same core idea in different words3:

Any observed statistical regularity will tend to collapse once pressure is placed upon it for control purposes.

Goodhart’s Law highlights a phenomenon that we often overlook:

When we try to incentivize a behavior with a measurable target, we tend to focus so much on achieving the measure that we lose sight of the object we had in mind.

Here are some examples:

  • Education: Grades can make students focus on their tests rather than developing deep knowledge about each subject.
  • Health care: Rating systems can make hospitals decline sick people, as those patients are more likely to lower the hospital ranking.
  • Politics: Approval ratings can make politicians focus on being likable rather than getting meaningful changes done.

I could list many more examples here, but you get the point: Incentives often lead to unexpected and unwanted results.

Some Personal Examples

I’m a big fan of habit tracking, and I’ve been doing it for many years.

It’s a behavior change strategy that has generally served me very well.

But not always.

For instance, I’ve sometimes found that measuring my meditation habit can be problematic.

One of the reasons I meditate is to relieve stress, and the risk of ruining my meditation streak can actually become quite stressful.

So, on more than one occasion, I’ve found myself stressing over a habit that’s supposed to reduce my stress. 🤦

I’ve also been guilty of things like:

  • Decreasing my productivity by doing the easiest tasks first.
  • Putting my health at risk by running with cold symptoms.
  • Ruining my focus by rising early after a poor night’s sleep.

… Just to add checkmarks to my to-do list and keep my habit streaks going.

Not a very wise approach.

How to Leverage Goodhart’s Law

Goodhart’s Law teaches us that we can’t expect to improve something just because we start measuring it.

Incentives are way more complicated than that.

So, whatever you decide to measure, be aware of your tendency to “game the system.”

Continually review your progress and ask yourself if your target is really bringing you closer to the objective you have in mind.

If it’s not—tweak it or switch it out and try again.

Because unless the target is truly effective, even a perfect score can be perfectly useless.

Footnotes

  1. A Short History of Nearly Everything by Bill Bryson
  2. ‘Improving Ratings’: Audit in the British University System
  3. Problems of Monetary Management: The UK Experience