State-led exchanges like Minnesota's Mnsure outperformed the federal exchange in the most recent signup of individual health policies. (Star Tribune/The Minnesota Star Tribune)

Insurance enrollment via state-based health insurance exchanges such as Minnesota's MNsure held steady for 2018, while sign-ups declined about 5 percent across the much larger group of states using the federal government's HealthCare.gov website.

The findings by the National Academy for State Health Policy raise a question about whether the intensity of outreach campaigns contributed to the difference, since the Trump administration limited marketing for the federal exchange while MNsure and other state-based groups maintained efforts.

Also called marketplaces, the exchanges were launched for 2014 as part of the federal Affordable Care Act (ACA), which created the websites to help consumers buy coverage and tap federal tax credits.

"Despite all the uncertainty and challenges we have seen, particularly for consumers living in states supported by state-based marketplaces, we see millions of Americans continuing to benefit from the coverage they got in the individual market," Trish Riley, executive director of the National Academy for State Health Policy, said in a statement.

The federal Centers for Medicare and Medicaid Services, which runs HealthCare.gov, did not comment on the report. A spokesperson for the agency said the open-enrollment period, which concluded in December for the federal exchange, was the most cost-effective sign-up period thus far, with high consumer satisfaction and a smooth enrollment experience.

For 2018, MNsure saw 116,358 plan selections, a new high for the exchange and a growth of about 1 percent compared with the year-ago open enrollment period.

The report released Wednesday shows a growth rate of nearly 6 percent for MNsure because the plan selection tally for 2017 doesn't reflect sign-ups through a special enrollment period last year that MNsure offered to consumers seeking one-time rebates provided by the state government.

After adjusting the report's numbers for those extra 2017 sign-ups, the number of enrollees for 2018 via state-based exchanges, including those run in partnership with HealthCare.gov, were essentially unchanged at roughly 3.47 million people. In partnership exchanges, states are responsible for outreach efforts, but direct shoppers to the federal website.

States that let the federal government control all aspects of their insurance exchange saw an aggregate decrease of 5.3 percent in plan selections, to about 8.29 million people, according to the report.

"The difference ... is even larger when comparing the changes in enrollment over the two-year period from 2016 to 2018," the policy group said in a statement. "Over the two-year period, while the enrollment in [federal exchange] states declined by 10.5 percent, enrollment in ... state-based marketplaces increased by 1.5 percent."

Overall, individual market enrollment via all exchanges for 2018 came in at more than 11.7 million, a decline of nearly 4 percent. The report found that 15 states including Minnesota saw year-over-year increases in plan selections during the open enrollment period.

In addition to spending more money on outreach efforts, state-based exchanges tend to run longer open enrollment periods for 2018 coverage. In Minnesota, enrollment was likely helped by a reinsurance program funded by the state government that helped keep a lid on premium growth.

"Minnesota is an example that reinsurance works to stabilize markets," said Allison O'Toole, the MNsure chief executive, in a statement. "But Minnesota's state-funded reinsurance program is just a band aid, and we need a long term federal reinsurance program to help Americans across the country."

It stands to reason that outreach and enrollment may have made a difference, but there likely are other factors at play, said Katherine Hempstead of the Robert Wood Johnson Foundation. State-based exchanges are probably less likely, Hempstead said, to be located in low-density population areas that are less hospitable for the individual market.

"It would seem that the sustained outreach efforts of states that run their own exchanges contributed to their success in maintaining or even increasing enrollment this year," Cynthia Cox, a researcher at the Kaiser Family Foundation, said in an e-mail. "There are also likely some state-specific factors that are at play here."

There were questions about how demand for individual market coverage in 2018 would be affected by Republican attempts to repeal and replace the ACA, which includes a requirement for most to have health insurance or pay a tax penalty. The law still stands, but the tax penalties for lacking coverage will go away in 2019.

Christopher Snowbeck • 612-673-4744 Twitter: @chrissnowbeck