Enrollment increases in the federal health insurance exchange during the most recent open season far outpaced growth in exchanges run by states, according to a new analysis.

Enrollment in the federal exchange, which is offered to eligible individuals in the 37 states that declined to set up exchanges authorized by the health care reform law, jumped 61% to 8.8 million at the close of the 2015 open season, according to the analysis released Tuesday by Washington-based consultant Avalere Health L.L.C.

By contrast, enrollment in the 13 states and the District of Columbia that run their own exchanges increased just 12% to 2.8 million.

Especially big enrollment growth in the federal exchange occurred in very large states with high uninsured rates. In Florida, which had 20% of its population uninsured in 2013 — the third highest of any state, according to the U.S. Census Bureau — 2015 enrollment climbed to 1.6 million people, a 62% increase, according to Avalere.

That made Florida the state with the highest number of enrollees in the federal exchange.

Similarly, in Texas, which in 2013 had the highest uninsured rate of any state at 22.1%, about 1.2 million people enrolled in the federal exchange in 2015, a nearly 64% increase over the prior year.

By contrast, in several big state-run exchanges, enrollment increases were much more modest. In California, the state with the largest exchange, enrollment at the close of the 2015 open season rose by only 1% to 1.4 million, while in New York, enrollment increased by about 10% to just over 400,000.

“Federally facilitated exchange states significantly outperformed their state-run counterparts in 2015,” Caroline Pearson, an Avalere senior vice president in Washington, said in a statement.

However, that surging growth in the federal exchange could quickly come to an end depending on the outcome of a case now before the U.S. Supreme Court.

The high court justices are expected to rule by the end of the current term in late June on whether the Affordable Care Act permits subsidies to eligible individuals seeking coverage in both federal and state exchanges, as authorized under 2012 Internal Revenue Service regulations.

Plaintiffs in the case say the law only allows premium subsidies in state-run exchanges.