One of those new issuers is Physicians Health Plan, the insurance arm of a community health system in Lansing, Michigan, called Sparrow Health.
PHP, which already sold employer-based plans and Medicaid plans, stayed out of the Obamacare market last year in part because of uncertainty about it, as well as the need to deal with other issues first, according to Dennis Reese, the insurer's interim CEO.
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"We were prepared to file [rates] last year, and in fact we did all the preparation, and then in the end we determined we are not going forward," Reese said.
But PHP decided to join HealthCare.gov, the federally run market that serves Michigan and 37 other states, this year. The insurer will be offering 12 separate health plans in eight Lansing-area counties.
"We believe that the exchanges are the wave of the future," Reese said. "We determined that we definitely need to be in the exchange, and it looks like it's going to stay, in some form."
Reese said PHP's premiums are higher than some competitors and lower than others. Michigan residents overall are faced with proposed Obamacare rate hikes of just 0.2 percent, on average, according to PwC.
But Reese said, "I think it's too early to tell" whether Michigan, or other states, will continue to see moderate average price increases in the future.
One reason was "the rates had to be put in before there was really any sound experience on what to base those rates on," Reese said, echoing Connolly. "Right now, it's people's best estimate."
But if those premiums aren't high enough to cover the costs of benefits paid out to enrollees, insurers will have to raise them in coming years, possibly by a much greater amount than they did for 2015.
Another reason rates might rise significantly higher in the future is that two out of the three Obamacare programs that are designed to financially protect insurers from the risks of enrolling too many sick people and not enough healthy people are set to expire after 2016.
Once those programs and the monetary cushion they provide go away, some insurers might be compelled to increase premium prices more aggressively than their competitors.
"That all has to be played out," Reese said.
But he noted that the current presence of those risk-protection programs is one of the reasons that PHP expects it is important to get on the Obamacare exchange now instead of later.