Despite much hand-wringing over the size and quality of provider networks on the health- insurance marketplaces established  under the Affordable Care Act, many top-notch hospitals are available in-network in marketplace plans this year, a new study found. However, more than half of those hospitals participated in fewer plans than last year, limiting their in-network availability to just one marketplace plan in a growing number of cases.

The analysis by the Robert Wood Johnson Foundation examined the marketplace plan participation in 2015 and 2016 of 156 hospitals that were highly ranked on U.S. News and World Report’s most recent list of Best Regional Hospitals based on clinical care and other measures.

Overall, the study found that more than 95 percent of highly rated regional hospitals were available in at least one marketplace plan in both years.

Following reports of marketplace plans with narrow provider networks and declines in the number of preferred provider organization plans with out-of-network coverage, “some people were starting to say that marketplace coverage is second-tier coverage,” said Katherine Hempstead, who leads the foundation’s work on health insurance coverage and authored the study. The analysis showed that marketplace plans are “not so dissimilar from employer-sponsored insurance,” she said. “The cost-sharing might be more aggressive [in marketplace plans], but they’re not that dissimilar.”

Whether they’ll stay that way remains to be seen, however. The proportion of hospitals that were in-network with just one marketplace plan nearly tripled between 2015 and 2016, from 7 percent to 20 percent, the analysis found. Fewer than half of hospitals — 43 percent — maintained or increased their participation from one year to the next.

“There’s a noticeable change between last year and this year,” Hempstead said.

States with big declines in marketplace plan participation by highly rated regional hospitals included Florida, Texas, Illinois, Virginia and Pennsylvania. In about a third of the states, however, participation stayed the same or increased. These included Arkansas, Rhode Island and the West Coast states of California, Washington and Oregon.

The data can’t tease out whether the declines in plan participation occurred because an insurer left the marketplace or because an insurer and hospital couldn’t reach an agreement on rates that the hospital was willing to accept, Hempstead said.