It now looks pretty clear that insurers are having a very bad experience in these markets. The sizeable premium increases would have been even higher if insurers had not stepped up the deductibles and clamped down on provider networks. The future of Obamacare now looks like more money for less generous coverage than its architects had hoped in the first few years.

But of course, that doesn’t mean insurers need to leave the market. Insurance is priced based on expectations; if you expect to pay out more, you just raise the price. After all, people are required to buy the stuff, on pain of a hefty penalty. How hard can it be to make money in this market?

What UnitedHealth’s action suggests is that the company is not sure it can make money in this market at any price. Executives seem to be worried about our old enemy, the adverse selection death spiral, where prices go up and healthier customers drop out, which pushes insurers’ costs and customers’ prices up further, until all you’ve got is a handful of very sick people and a huge number of very expensive claims.