The story
Named after British economist Charles Goodhart (1936–), who originated it.
Etymology from Wiktionary, CC BY-SA 4.0.
Goodhart's law
Today it means: The idea that, when a measure becomes a target, it ceases to be a good measure; originally, "as soon as the government attempts to regulate any particular set of financial assets, these become unreliable as indicators of economic trends". Full definition →