New York, which like California runs its own enrollment system, saw modest growth with about 407,000 enrolled, 37,000 more than a year ago, in a state with 1.8 million uninsured people. In California, enrollment was flat, with about 1.4 million signed up -- the same as in 2014.

In the 37 states that used the U.S.-run website, growth in sign-ups from 2014 to 2015 ranged from 25 percent to 81 percent, according to Gaba. Among states that run their own exchanges, only Massachusetts and Hawaii did better -- in part because those two states struggled with technology failures in 2014.

Medicaid may be one reason why. Any comparison of enrollment in California and Florida should include people in the program for low-income people, said Dana Howard, a spokesman for Covered California, the state’s Obamacare agency.

California and New York both expanded Medicaid to cover the working poor in 2014. Florida, Georgia, North Carolina and 19 other states didn’t, and as a result some low-income adults in those places who would have been eligible for Medicaid are instead enrolled in private coverage. California’s uninsured population has been halved since last year, including its Medicaid expansion, Howard said.

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