Goodhart's Law
Origin
First stated by UK central bank economist Charles Goodhart in 1975 monetary policy papers. The M3 money supply was a good inflation predictor — but the moment government targeted M3, the relationship broke because markets routed around the measure. Anthropologist Marilyn Strathern in 1997 refined the general form: "When a measure becomes a target, it ceases to be a good measure."
Meaning
Make average test scores a school KPI, and teachers leak exam content, mark weak students absent, and inflate grades. Make revenue the only KPI, and sales push reckless discounts. A measure's essence is signal, not target — once it becomes a target, the system camouflages the signal.
Lesson — Meeting Eastern Classics
Tao Te Ching 1: "The Tao that can be spoken is not the eternal Tao." Zhuangzi taught the limit of all measurement. Goodhart's Law is the place where the Way becomes measurable and ceases to be the Way.
"標" combines tree (木) with mark (票) — originally a marker on a tree, a target. A marker points the way; it is not the way. Goodhart's Law mistakes 標 for 道. Cling to the marker, lose the path.
