When a measure becomes a target

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Calling Bullshit: The Art of Scepticism in a Data-Driven World by Jevin D. West, Carl T. Bergstrom

The rankings ended up being influenced as much by admissions departments’ willingness to chase metrics as they did by the quality of schools’ applicants. This problem is canonized in a principle known as Goodhart’s law. While Goodhart’s original formulation is a bit opaque,*8 anthropologist Marilyn Strathern rephrased it clearly and concisely: When a measure becomes a target, it ceases to be a good measure. In other words, if sufficient rewards are attached to some measure, people will find ways to increase their scores one way or another, and in doing so will undercut the value of the measure for assessing what it was originally designed to assess.

So if you sample instructors at random, you are likely to observe a large class or a small class in proportion to the frequency of such classes on campus. In our example above, there are more teachers teaching small classes. But large classes have many students and small classes have few, so if you sample students at random, students are more likely to be in large classes.*5 Recall from chapter 5 Goodhart’s law: “When a measure becomes a target, it ceases to be a good measure.” Class sizes provide an example. Every autumn, college and university administrators wait anxiously to learn their position in the U.S. News & World Report university rankings. A higher ranking improves the reputation of a school, which in turn draws applications from top students, increases alumni donations, and ultimately boosts revenue and reputation alike.

Significant results are strongly overrepresented in the literature, and nonsignificant results are underrepresented. The data from experiments that generated nonsignificant results end up in scientists’ file cabinets (or file systems, these days). This is what is sometimes called the file drawer effect. Remember Goodhart’s law? “When a measure becomes a target, it ceases to be a good measure.” In a sense this is what has happened with p-values. Because a p-value lower than 0.05 has become essential for publication, p-values no longer serve as a good measure of statistical support. If scientific papers were published irrespective of p-values, these values would remain useful measures of the degree of statistical support for rejecting a null hypothesis.

pages: 301 words: 78,638

Atomic Habits: An Easy & Proven Way to Build Good Habits & Break Bad Ones by James Clear

We teach for standardized tests instead of emphasizing learning, curiosity, and critical thinking. In short, we optimize for what we measure. When we choose the wrong measurement, we get the wrong behavior. This is sometimes referred to as Goodhart’s Law. Named after the economist Charles Goodhart, the principle states, “When a measure becomes a target, it ceases to be a good measure.” Measurement is only useful when it guides you and adds context to a larger picture, not when it consumes you. Each number is simply one piece of feedback in the overall system. In our data-driven world, we tend to overvalue numbers and undervalue anything ephemeral, soft, and difficult to quantify.

Missing twice is the start of a new habit.” I swear I read this line somewhere or perhaps paraphrased it from something similar, but despite my best efforts all of my searches for a source are coming up empty. Maybe I came up with it, but my best guess is it belongs to an unidentified genius instead. “When a measure becomes a target”: This definition of Goodhart’s Law was actually formulated by the British anthropologist Marilyn Strathern. “‘Improving Ratings’: Audit in the British University System,” European Review 5 (1997): 305–321, https://www.cambridge.org/core/journals/european-review/article/improving-ratings-audit-in-the-british-university-system/FC2EE640C0C44E3DB87C29FB666E9AAB.

pages: 339 words: 105,938

The Skeptical Economist: Revealing the Ethics Inside Economics by Jonathan Aldred

Any government adopting an explicit, overarching policy of maximizing perceived happiness must confront its relationship with democratic politics. As I have argued, the Greatest Happiness principle cannot stand above politics. Another problem is what economists call Goodhart’s Law.9 A succinct definition is: ‘when a measure becomes a target, it ceases to be a good measure’. So once governments target aggregate measures of self-reported happiness, these measures cease to track ‘true’ happiness. Goodhart’s Law can be thought of as the application to human society of Heisenberg’s Uncertainty Principle in quantum physics. Put simply, measuring a system generally disturbs it.60 In human society, an important reason is that people manipulate data once it matters to them.

There is an optimistic view that these kinds of problems can be avoided by carefully chosen targets and incentive structures, but this view is not supported by most independent reviews of the audit culture.23 On the contrary, Goodhart’s Law (introduced in Chapter 5) is frequently mentioned: when a measure becomes a target, it ceases to be a good measure. Goodhart’s Law suggests that distortions and unintended consequences are an unavoidable part of any target regime. Once people or their activities are being targeted, their behaviour inevitably changes, either unintentionally or because they actively seek to manipulate the measurements.

pages: 184 words: 46,395

The Choice Factory: 25 Behavioural Biases That Influence What We Buy by Richard Shotton

From your perspective this was a rational decision, but it’s counter to your employer’s intention. They created the bonus system to boost income, but in this case it has reduced it. This poorly set target, which led to unintended consequences, is an example of Goodhart’s Law. This states: When a measure becomes a target, it ceases to be a good measure. One infamous example of unintended consequences is from Hanoi, Vietnam, during the spring of 1902. When faced with an outbreak of bubonic plague, the French colonialists offered a small fee for every rat’s tail handed in. The tactic seemed successful at first – tails began to pour in.

pages: 249 words: 77,342

The Behavioral Investor by Daniel Crosby

A similar incident was observed in India during the time of British colonial rule. A reward was set for every dead cobra and so enterprising Indians began to – you guessed it – raise cobras on snake farms. The Cobra Effect is now shorthand for what is officially referred to as Campbell’s’ Law, which states, “when a measure becomes a target, it ceases to be a good measure.” Campbell says of the tendency for measurement to corrupt efficacy, “The more any quantitative social indicator is used for social decision-making, the more subject it will be to corruption pressures and the more apt it will be to distort and corrupt the social processes it is intended to monitor.”

pages: 428 words: 103,544

The Data Detective: Ten Easy Rules to Make Sense of Statistics by Tim Harford

Social scientists have long understood that statistical metrics are at their most pernicious when they are being used to control the world, rather than try to understand it. Economists tend to cite their colleague Charles Goodhart, who wrote in 1975: “Any observed statistical regularity will tend to collapse once pressure is placed upon it for control purposes.”12 (Or, more pithily: “When a measure becomes a target, it ceases to be a good measure.”) Psychologists turn to Donald T. Campbell, who around the same time explained: “The more any quantitative social indicator is used for social decision-making, the more subject it will be to corruption pressures and the more apt it will be to distort and corrupt the social processes it is intended to monitor.”13 Goodhart and Campbell were onto the same basic problem: a statistical metric may be a pretty decent proxy for something that really matters, but it is almost always a proxy rather than the real thing.

Super Thinking: The Big Book of Mental Models by Gabriel Weinberg, Lauren McCann

If the output of nails was determined by their number, factories produced huge numbers of pinlike nails; if by weight, smaller numbers of very heavy nails. The satiric magazine Krokodil once ran a cartoon of a factory manager proudly displaying his record output, a single gigantic nail suspended from a crane. Goodhart’s law summarizes the issue: When a measure becomes a target, it ceases to be a good measure. This more common phrasing is from Cambridge anthropologist Marilyn Strathern in her 1997 paper “‘Improving Ratings’: Audit in the British University System.” However, the “law” is named after English economist Charles Goodhart, whose original formulation in a conference paper presented at the Reserve Bank of Australia in 1975 stated: “Any observed statistical regularity will tend to collapse once pressure is placed upon it for control purposes.”

pages: 410 words: 119,823