Goodhart's Law — a wooden ruler with an archery target and an arrow stuck in it

A telephone handset lying off the hook — Judged on call length, so they hang up

A thermometer measuring versus a thermometer held over a candle — targeting vs measuring

A measuring tape curled on itself — The number moves. Nothing else does.

镜背 · Back of the Lens

Goodhart's Law

22 August 2026

The law Once you reward people for moving a number, the number stops telling you what it used to. 一旦把一个数字用来考核，它就不再是原来那个指标了。

"Any observed statistical regularity will collapse once pressure is put on it for control purposes."

Origin Charles Goodhart, Bank of England adviser, 1975 — those were his actual words. 查尔斯·古德哈特，英格兰银行顾问，1975年，原话如此。

In practice Call centres judged on call length learn to hang up. 以通话时长考核客服，他们就学会挂电话。 Schools judged on test scores learn to teach the test. 以考试成绩考核学校，他们就学会押题。

Who actually said it The famous phrasing everyone quotes is not his. 那句广为流传的表述，不是他写的。 The anthropologist Marilyn Strathern wrote it in 1997. 是人类学家玛丽莲·斯特拉森1997年写的。

Common misuse The law gets used lazily — as a reason to measure nothing at all. 这条规律常被懒用，成了"干脆别量"的借口。

自己的理解说白了，一旦拿它考核你，你就会去对付那个数字，不是去做那件事。这条我经常犯。但也别走反了——不量就什么都不知道。