Some health policy experts like Joseph Antos of the American Enterprise Institute contend that premiums won't rise dramatically, since they have to be approved by state insurance commissioners, who have been under political pressure to keep premiums low. That pressure is only likely to increase next year, in an election year.
Before the passage of the Affordable Care Act, rates ebbed and flowed with the market, Antos said but "it's hard to be a state commissioner now and not take an interest in premiums."
Yet even if premiums shot up for 2015, many consumers on the new marketplace may not even notice because the extra cost would be covered by the government.
Subsidies for the exchange will be available to individuals with household incomes between 100 and 400 percent of the federal poverty level -- taking into account factors like family size. According to the Kaiser Family Foundation, 52 percent of people on the marketplace are expected to qualify for subsidies (another 38 percent will qualify for Medicaid, a government program, leaving only 10 percent of enrollees without any government assistance).
Those who qualify for subsidies will only have to pay a certain percentage of their income -- those at 100 percent of the poverty level will only pay 2 percent of their income, while those at 400 percent will pay 9.5 percent of their income. In other words, premium costs that exceed those levels will be paid for by the government. It may come at a cost to taxpayers, but consumers on the market won't be driven away by skyrocketing premiums.
Along with subsidies, there are other mechanisms built into the Affordable Care Act designed to prop up the new individual health insurance market. For instance, the "reinsurance" program taxes all insurance plans -- including employer-provided insurance -- and reimburses the individual market for its high-risk enrollees. The reinsurance program is pumping $10 billion into the marketplace.
"If insurers end up with high claims, part of that is paid for with this," Levitt explained.
Additionally, insurers can rely on "risk corridors," which enable the government to share in the risks and gains of the marketplace. If the cost of insuring people is lower than expected, insurers pay into a pool, and if it's higher than expected, they can draw from that pool.
"The expectation is that it'd even out, but it is possible if a much sicker group of people enrolled, there could be a cost to taxpayers," Levitt said. However, if this were the case, the net total cost to taxpayers could even out, Levitt explained -- a smaller market could mean an expense in the risk corridor, but it would also mean the government would be paying out less in subsidies.
Rather than raising premiums, insurers could simply abandon a weak marketplace. Levitt, however, said it's unlikely that the market would collapse that quickly.
"Even if enrollment is low at first, the potential market is still quite large," he said. "My guess is that the major insurers would stick it out... Everyone's expectations for enrollment in the first year are modest to begin with."
That said, he added, "The first month hasn't quite gone quite as expected, either."