Wednesday, February 02, 2011

More on the concept expressed by Goodhart's law

Calling it "teaching to the test" or ...

John Goodman asks the question "Does measuring quality actually decrease quality?". See here for his recent blog entry.

Charles Goodhart, a British economist put it this way in 1975:

Any observed statistical regularity will tend to collapse once pressure is placed upon it for control purposes

In other words, a measurement when used as a target looses its value as a measure.

This basic notion was expressed about the same time by a sociologist, Donald Campbell, who said :

"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."

A poster child for this phenomenon in the context of quality measures in medicine is the absurd 4-hour pneumonia rule.I have blogged about that before.

When the incentive for ED staff was to get the antibiotics to pneumonia patients within 4 hours, because that was established as a quality measure, distortion and corruption emerged in the form of giving less prompt attention to non-pneumonia suspects and treating folks who really didn't have pneumonia with antibiotics.

From Goodman's post:

Quality measures also degrade quality by distorting behavior.

Dr. Douglas Perednia had a great discussion of this topic here.

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