SOCIAL SCIENCE CONCEPT

What Is Campbell's Law? Why Metrics Corrupt What They Measure

You measure teacher performance by test scores. Teachers teach to the test. Students learn less. The metric corrupted the goal. That is Campbell's Law.

Editorial illustration of a teacher teaching to a test while students suffer

Creator Donald T. CampbellOrigin Social PsychologyYear 1975Category Psychology, Sociology

QUICK ANSWER

Here is the idea in plain English.

Campbell's Law states that the more a social indicator is used for decision-making and control, the more it is subject to corruption and the more it distorts the process it is meant to measure. It was formulated by Donald T. Campbell in 1975. The law is closely related to Goodhart's Law. It explains why performance metrics often backfire in education, healthcare, and government.

If you remember only a few things, remember these.

The basic move

Campbell's Law is simple: when you use a metric to control something, it corrupts what you are trying to measure. If you measure schools by test scores, teachers teach to the test. The test scores go up. The students do not learn more.

Why it matters

The same thing happens in healthcare. If you measure hospitals by patient satisfaction, they prescribe unnecessary opioids. The satisfaction scores go up. The patients suffer.

Use it deliberately

When creating a metric, ask: how will people game it? What behavior will it incentivize?

CORE IDEA

The concept in its simplest useful form.

What Does Campbell's Law Mean in Simple Terms?

The same thing happens in healthcare. If you measure hospitals by patient satisfaction, they prescribe unnecessary opioids. The satisfaction scores go up. The patients suffer.

The law warns that metrics are not neutral. They change behavior. The behavior change often undermines the original goal.

The small mechanism underneath the big idea.

The Story Behind Campbell's Law

Donald T. Campbell was a psychologist and social scientist. In 1975, he wrote about the problems of using social indicators for decision-making. He noticed that when a metric is used for control, it distorts the process it is meant to measure.

Campbell's most famous example was education. If you measure schools by test scores, teachers will teach to the test. Students will learn less. The metric corrupts the goal.

Campbell's Law is closely related to Goodhart's Law. Both warn about the dangers of metrics. Campbell applied the insight to social policy.

Why Campbell's Law Became Famous

Campbell's Law became famous because it explains a common problem: performance metrics backfire. The law is widely cited in education, healthcare, and public policy.

The concept is closely related to Goodhart's Law. Both warn about the dangers of metrics. Campbell applied the insight to social policy.

Today, Campbell's Law is a foundational concept in evaluation and measurement. It is taught in schools of public policy and education.

Diagram showing how metrics corrupt the processes they are meant to measure — A diagram showing the cycle of metric corruption: metric created, behavior changes, metric improves, goal is undermined.

Where this idea shows up outside the textbook.

Education

Schools are measured by test scores. Teachers teach to the test. Students learn less. The metric corrupts the goal.

Healthcare

Hospitals are measured by patient satisfaction. They prescribe unnecessary opioids. The metric corrupts the goal.

Government

Agencies are measured by performance indicators. They game the system. The metrics improve. The goals are not met.

Business

Employees are measured by call duration. They rush calls. Customer satisfaction drops. The metric corrupts the goal.

CONCEPT MAP

Every idea has neighbors. This is where the current concept sits in the TinyThat knowledge graph.

Current concept

Campbell's Law

The more a social indicator is used for control, the more it corrupts the process.

Strong link

Goodhart's Law

The closest general version of the same idea.

Strong link

Perverse Incentives

Bad targets create bad behavior.

Cobra Effect

A metric or reward can worsen the original problem.

RelatedComing soon

Teaching to the Test

A common education example.

What people often get wrong about this idea.

Campbell's Law is the same as Goodhart's Law.

They are closely related but different. Goodhart's Law is about economics. Campbell's Law is about social indicators.

Campbell's Law means metrics are useless.

No. It means metrics should be used carefully. They are tools, not goals.

Campbell's Law only applies to education.

No. It applies to any social indicator used for control. Healthcare, government, and business are all vulnerable.

Useful ideas become dangerous when they are stretched too far.

Criticisms and Limitations of Campbell's Law

Campbell's Law is a powerful concept, but it has limitations. Not every metric corrupts the goal. Some metrics are well-designed.

The law can be misused to avoid accountability. Some people use it to resist measurement. The solution is better measurement, not no measurement.

The law is a heuristic, not a law of nature. It is a guide, not a rule.

Three simple ways to apply the idea without turning it into a slogan.

When creating a metric, ask: how will people game it? What behavior will it incentivize?

Use multiple metrics

Use multiple metrics. Do not rely on a single number. The more metrics, the harder it is to game.

Be skeptical of improvements

Be skeptical of improvements. A metric that goes up might not mean things are better. It might mean people are gaming the system.

EXPLORE NEXT

The best next ideas to read after this one.

Quick answers to common questions.

What is Campbell's Law in simple terms?

When you use a metric to control something, it corrupts what you are trying to measure. The metric becomes the goal. The original goal is lost.

What is an example of Campbell's Law?

Schools are measured by test scores. Teachers teach to the test. Students do not learn more. The metric corrupted the goal.

How do you avoid Campbell's Law?

Use multiple metrics. Be skeptical of improvements. Understand that metrics create incentives.

Why is Campbell's Law a problem?

It leads to gaming, corruption, and unintended consequences. The metric becomes the goal. The original goal is lost.