The people who could lose their health insurance as a result of a Supreme Court decision this year are predominantly white, Southern, employed and middle-aged, according to an Urban Institute analysis.

The case, called King v. Burwell, concerns whether federal subsidies that help middle-income Americans buy their health insurance can be distributed in every state, or just those that are running their own marketplaces. A ruling for the challengers could mean that residents of more than 30 states would lose subsidies. Some would be immediately priced out of the market. Others would be expected to lose coverage later, after insurers raised prices to account for the change. The Urban Institute analysis estimated that, over all, two-thirds of people receiving subsidies would drop coverage if those subsidies disappeared, and a quarter of people paying their entire premiums would also become uninsured.

The Affordable Care Act helped about 10 million Americans obtain health insurance last year — and more people have signed up for the law’s coverage programs in the last few months. But not everyone who has such insurance would be affected if the Supreme Court ruled for the plaintiffs. Its effects would be limited to residents of certain states and certain income groups.