Millions of Americans in the past few years have run into this experience: filing a health insurance claim that once might have been paid immediately but instead is just as quickly denied. If the experience and the insurer's explanation seem arbitrary and absurd, that might be because companies appear increasingly likely to employ computer algorithms or people with little relevant experience to issue rapid-fire denials of claims—sometimes bundles at a time—without reviewing the patient's medical chart. A job title at one company was "denial nurse."

It's a handy way for insurers to keep revenue high—and just the sort of thing that provisions of the Affordable Care Act (ACA) were meant to prevent. Because the law prohibited insurers from deploying previously profit-protecting measures, such as refusing to cover patients with pre-existing conditions, the authors worried that insurers would compensate by increasing the number of denials.