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Goodhart's Law

Also Known As: Campbell's Law metric gaming teaching to the test cobra effect
Statistical Error ID: goodharts_law

Definition

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.

Examples

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.

A school district ties teacher evaluations to student scores on standardized reading tests. Teachers begin dedicating nearly all class time to test-format drills, cutting out creative writing and critical discussion. Test scores rise, but broader literacy and love of reading decline.

A software company measures developer productivity by number of commits per week. Developers respond by breaking single logical changes into dozens of tiny, trivial commits. Commit counts soar while actual feature delivery slows down.

Verification Steps
Verification Steps
Binary yes/no questions that an AI must answer to detect a reasoning pattern in a text.
Each of the 452 aspects has verification steps — simple yes/no questions designed to systematically detect whether a pattern appears in a text. For ad hominem: "Does the argument attack a person rather than their claim?" For false dichotomy: "Are only two options presented when more exist?" This ensures consistent, reproducible analysis.

Binary (yes/no) questions an LLM must answer to identify this aspect:

  1. 1

    Has a statistical measure been adopted as an explicit target or incentive?

    Type: binary
  2. 2

    Are people gaming or optimizing for the metric rather than the underlying objective?

    Type: binary
  3. 3

    Has the measure's relationship to the actual goal degraded since it became a target?

    Type: binary
  4. 4

    Are there signs of metric manipulation rather than genuine improvement?

    Type: binary
Deep Dive
The expandable detail section on each aspect page with examples, psychology, and counter-strategies.
The Deep Dive section provides in-depth information about each aspect: a real-world example showing the pattern in action, an explanation of why it works psychologically, practical advice on how to counter it, alternative names, and links to related aspects.

Hierarchical Context