But yesterday, Politico published a long article giving more support to the “gaming” hypothesis. People who sign up during special enrollment, insurers say, “run up much higher medical bills and then jump ship, contributing to double-digit rate increases and financial losses.” Customers are also exploiting the three-month “grace period” when they can stop paying premiums and still get treatment from providers. And the article suggests that at least some Americans have realized that under current regulations, they need to be insured for only nine months of the year to avoid the mandate penalty. So you can sign up for insurance, cram all your spending into that shorter time frame, and then stop paying for the last three months.

This is not just UnitedHealth, either. Blue Cross Blue Shield, the mainstay of the marketplaces, appears to be seeing similar problems, as does Aetna. This is not just the experience of one outlier.

I don’t want to overstate the threat here. But I really can’t. Unless it’s gotten under control, this sort of behavior poses an existential threat to the exchange marketplaces. The more people game the system, the more people will have to game the system. People who game both incur more in costs than regular consumers do and pay less in premiums, which means everyone else has to pay more. As the insurance gets more expensive, those regular consumers will be increasingly tempted to convert to gamers themselves, and the marketplaces may well collapse.