There are downsides to this strategy, of course. One is that it may be hard for patients who have complex health needs to find the care that they need with every plan. The other is that it could create a lot more disruptions in care for people, if they have to switch plans — and all their doctors — every year in order to get a good price on insurance. In the long run, insurers may have to find other ways to lower costs, like keeping customers healthier.

Another, simpler way to bring down prices would be to get more healthy people into the market, so the average insurance customer costs less, or use other tools to absorb the cost of people with complicated and expensive medical conditions. (See below.)

The market is too small

The problem: There are currently about half as many people in the exchanges as the Congressional Budget Office expected.

Why it’s a problem: About 27 million Americans still don’t have insurance, a bad thing by itself in a country where health insurance is often crucial to ensuring access to health care and protection from financial ruin. But too few customers also matter for the functioning of the market. Smaller markets make it hard for insurers to absorb the costs of a few sick patients. In some places — especially big cities — there are still enough people to spread out risk. But in many parts of the country, too few healthy people are signing up to balance the cost of those needing expensive medical care. And it means that, especially if a company is having trouble making money, there’s not a lot of upside to sticking around.

Possible solutions: Change the incentives, so more people who are currently uninsured buy health insurance. Hillary Clinton has talked about giving out more generous subsidies, so insurance costs less and more people can afford to buy it. Many Republican politicians suggest another way to lower prices: eliminating current requirements that insurance cover a wide array of services. Some policy experts, including Uwe Reinhardt, a Princeton health economist, in a recent Vox.com interview, have suggested tightening up the penalties for remaining uninsured, so people can’t wait and buy insurance only after they get sick.

A more controversial way to increase enrollment in the marketplaces would be to make employer coverage less attractive, so that more people who currently have insurance from work switch to buying their own. It was widely expected that this would happen as the law rolled out, but so far it hasn’t.