Goodhart's Law — When Numbers Lie

Has this ever happened to you? A call center sets 'average call duration' as a key performance indicator, targeting shorter calls.

Also known as: Campbell's Law, metric gaming, teaching to the test, cobra effect

What's Actually Happening

Goodhart's Law states that when a measure becomes a target, it ceases to be a good measure. Once people know they are being evaluated by a specific metric, they optimize for that metric rather than the underlying goal it was intended to represent. This creates perverse incentives where the metric improves while the actual desired outcome deteriorates or remains unchanged.

Metrics are simplifications of complex realities. Optimizing for the simplified proxy is almost always easier than optimizing for the underlying complex goal, so rational actors will game the metric.

Real Talk: You See This Every Day

A call center sets 'average call duration' as a key performance indicator, targeting shorter calls. Agents begin rushing customers, transferring difficult calls, or hanging up before resolution. Average call time drops, but customer satisfaction plummets and repeat calls increase.

Goodhart's Law manifests in standardized testing (teaching to the test), policing (crime statistic manipulation), scientific publishing (citation gaming), and social media (engagement metric optimization).

Your BS Detector

Use multiple complementary metrics that are harder to game simultaneously. Regularly rotate or update metrics, and include qualitative assessments alongside quantitative ones.

• ✓ Who collected this data, and why?
• ✓ Is the sample big enough and fair?
• ✓ Could there be another explanation?

The Challenge

Next time someone throws a statistic at you — in class, online, in the news — don't just accept it. Ask: what's missing from this picture?

Part of the TellDear Teen Book — criticalthinking.guide