Abstract

There are several distinct failure modes for overoptimization of systems on the basis of metrics. This occurs when a metric which can be used to improve a system is used to such an extent that further optimization is ineffective or harmful, and is sometimes termed Goodhart’s Law11 1 As a historical note, Goodhart’s Law [1] as originally formulated states that “any observed statistical regularity will tend to collapse once pressure is placed upon it for control purposes.” This has been interpreted and explained more widely, perhaps to the point where it is ambiguous what the term means. Other closely related formulations, such as Campbell’s law (which arguably has scholarly precedence[3]) and the Lucas critique, were also initially specific, and their interpretation has also been expanded greatly. Lastly, the Cobra Effect and perverse incentives are often closely related to these failures, and the different effects interact. Because none of the terms were laid out formally, the categories proposed do not match what was originally discussed. A separate forthcoming paper intends to address the relationship between those formulations and the categories more formally explained here.. Th