Goodhart's law

[1] It is named after British economist Charles Goodhart, who is credited with expressing the core idea of the adage in a 1975 article on monetary policy in the United Kingdom:[2] Any observed statistical regularity will tend to collapse once pressure is placed upon it for control purposes.

[3]It was used to criticize the British Thatcher government for trying to conduct monetary policy on the basis of targets for broad and narrow money,[4] but the law reflects a much more general phenomenon.

Jerome Ravetz's 1971 book Scientific Knowledge and Its Social Problems[8] also predates Goodhart, though it does not formulate the same law.

While it originated in the context of market responses, the law has profound implications for the selection of high-level targets in organizations.

Goodhart's law [...] states that when a feature of the economy is picked as an indicator of the economy, then it inexorably ceases to function as that indicator because people start to game it.Later writers generalized Goodhart's point about monetary policy into a more general adage about measures and targets in accounting and evaluation systems.

It was that conflation of 'is' and 'ought', alongside the techniques of quantifiable written assessments, which led in Hoskin's view to the modernist invention of accountability.