Where it sits
The law describes the transition, not either end state.
Tell it apart
| Aspect | Goodhart's law | North Star Metric |
|---|---|---|
| Says | Targets corrupt measures | Pick one measure as target |
| Stated | 1975 | 2010s |
| Aware of the other | n/a | Usually not |
| Both can be right | Briefly | Briefly |
| Timescale | Bites later | Works at first |
| Remedy | Use several | Change it periodically |
The North Star Metric is Goodhart's Law's most confident modern violation. Naming one number as the target is exactly the pressure Goodhart described — the practice and the warning are the same sentence read in opposite directions.
What it doesn't mean
He did not. That phrasing is Marilyn Strathern's, from a 1997 paper on British university audit. Goodhart's own 1975 sentence is about statistical regularities collapsing under control pressure — and it was about MONETARY POLICY, not management.
Campbell's law, addressing the corruption of quantitative social indicators, has formulations dating to 1969 — six years earlier. The idea has been independently discovered several times, which is usually a sign it is true.
What it really means
The most-quoted sentence in modern management is attributed to the wrong person, in the wrong field, about the wrong subject.
When a measure becomes a target, it ceases to be a good measure — that is Marilyn Strathern, an anthropologist, writing in 1997 about audit in British universities.
What Charles Goodhart actually wrote, in 1975, in a paper on UK monetary management, is:
Any observed statistical regularity will tend to collapse once pressure is placed upon it for control purposes.
Denser, and considerably more precise. Goodhart was describing something specific to central banking: the Bank had noticed a stable relationship between a money-supply measure and inflation, and started targeting the measure. The relationship stopped holding. Not because anyone cheated — because the relationship had been a by-product of behaviour that nobody was steering, and steering it changed the behaviour.
That is the deeper claim, and it survives the loss of the catchphrase. A measure works as a proxy because of how it is generated. Target it, and you change the generating process — so the proxy is now measuring the response to being measured.
And Goodhart was not first. Campbell's law, on the corruption of quantitative social indicators, has formulations from 1969 — six years earlier. Which is itself informative: an idea that a psychologist and an economist arrived at independently, six years apart in unrelated fields — and that an anthropologist later gave its most quoted form — is usually describing something real.
One practical note. The slogan invites the response so don't use metrics, which is useless. A 2018 paper identifies at least four distinct failure mechanisms under the law — and they need different fixes. Knowing which one you have is the difference between a repairable measurement system and a slogan you repeat while it degrades.
Where it comes from
Charles Goodhart, a Bank of England monetary economist
The version everyone quotes was written by an ANTHROPOLOGIST about university audit, not by Goodhart about money.
- 1975
Charles Goodhart writes, in a paper on UK monetary management: 'Any observed statistical regularity will tend to collapse once pressure is placed upon it for control purposes.'
- 1997
Marilyn Strathern's paper on audit in the British university system supplies the memorable phrasing.
In real life
- A call centre rewards staff for short calls, so agents start ending difficult calls early: the average call time falls, and the service gets worse.
- A school judged on exam pass rates steers its weakest pupils away from sitting the exam. The pass rate rises, and stops telling anyone how well the school teaches.
- A software team rewarded for the number of bugs fixed starts logging trivial bugs to fix — the count soars while the product barely improves.
Questions
Q01What did Goodhart actually write?
That 'any observed statistical regularity will tend to collapse once pressure is placed upon it for control purposes' — written in 1975, about UK monetary management.
Q02Who wrote the famous version?
The anthropologist Marilyn Strathern, in a 1997 paper on audit in British universities. The line everyone attributes to an economist was written by an anthropologist about universities.
Q03Is there a taxonomy?
Yes — a 2018 paper identifies at least four distinct failure mechanisms, which is more useful than the slogan because different failures need different fixes.
Sources
- Goodhart's law — Wikipedia.
- Manheim & Garrabrant, Categorizing Variants of Goodhart's Law — arXiv:1803.04585.