Goodhart's Law
"When a measure becomes a target, it ceases to be a good measure." — Charles Goodhart, economist
Once you optimize for a metric, behavior shifts toward gaming the metric rather than achieving the underlying goal. The measurement stops tracking what it was measuring.
The Restaurant Example
A restaurant tracks daily revenue to judge whether the chef is doing a good job. If revenue is rising, food must be good. If revenue falls, something is wrong.
But revenue only tells part of the story. A dissatisfied customer is unlikely to dine and dash — they'll still pay. Revenue could be rising because of aggressive discounts or marketing while food quality quietly declines. The measure has drifted from the goal.
A better metric: percentage of customers who finish their meal. Percentage who leave a generous tip. These track the actual goal (food quality) more faithfully.
Where It Shows Up
- Fitness: Track steps → optimize for steps, not health. Walk in circles at home to hit 10,000.
- Work: Track hours → optimize for hours, not output. Look busy instead of being productive.
- Education: Teach to standardized tests → optimize for test scores, not learning, curiosity, or critical thinking.
- Business: Track quarterly earnings → optimize for quarterly earnings; defer maintenance, cut R&D, manipulate accounting.
- Habit tracking: Track the habit streak → break the spirit of the habit to preserve the number.
In each case, the metric starts as a proxy for the goal. Once the metric becomes the target, the proxy relationship breaks.
The Fix
Measurement is useful when it guides — when it adds context to a larger picture. It fails when it consumes — when the number becomes the purpose.
Practical responses:
- Track process, not only outcome. Did you do the habit? Not: did it produce the result today?
- Use multiple metrics. A single metric is easy to game; a bundle is harder.
- Rotate what you track. If the scale stops motivating, measure energy, sleep quality, or strength instead.
- Remind yourself of the underlying goal. What is the measure actually a proxy for?
Just because something is measurable doesn't make it the most important thing. And just because something is hard to measure doesn't mean it doesn't matter.
Connections
- habit-tracking — Clear's "pitfalls" section: tracking the wrong metric is a failure mode of habit tracking; Goodhart's Law is the underlying principle
- incentive-superpower — Munger's version of the same phenomenon: incentives reshape cognition; when the metric becomes the incentive, it reshapes what people notice and believe
- second-order-thinking — Goodhart's Law is a second-order effect: the first-order intention (measure the goal) produces a second-order consequence (the measure becomes the goal)