The analysis reflects the fact that some 85 percent of Obamacare customers who buy plans on government-run marketplaces receive federal subsidies, or tax credits, that reduce the amount they end up actually paying for their monthly premiums. That brings their payout below the retail prices. And the tax credits, which are available to people with low or moderate household incomes, go up in value as premium prices increase year over year.
That point is illustrated in the analysis, which found that if all premiums increased by 50 percent, even more HealthCare.gov customers would be able to find coverage for $75 or less, and $100 or less, than would be the case if the rate hikes were 25 percent. The report noted that even a 25-percent across the board hike is "highly unrealistic."
"Headline rate increases do not reflect what consumers actually pay," said Kathryn Martin, acting assistant secretary for planning and evaluation at the HHS, whose division conducted the analysis.
Last year, the report noted, the average premium for HealthCare.gov customers with a subsidy increased just $4 per month.
However, HHS' analysis leaves unspoken what will happen next year to Obamacare customers who are not eligible for subsidies, either because their incomes are too high or because they buy plans outside of HealthCare.gov or on exchanges operated by individual states.
About 11 million people are covered by individual health plans sold through government-run exchanges. Millions of more people buy plans outside of those marketplaces.
"Subsidy-eligible people are protected from rate increases, and nonsubsidy eligible people feel the brunt of those rate increases," said Caroline Pearson, senior vice president for policy and strategy at the Avalere Health consultancy.
"Certainly, non–subsidy eligible people are going to feel the full effect ... they're going to see higher rates in many cases this [next] year than they did in previous years," she said.
Many plans sold either on or outside the exchanges are proposing significantly higher increases for 2017 premiums than they have in recent years.
Blue Cross Blue Shield of Texas, which is HealthCare.gov's second-biggest biggest state in terms of customers, is asking for rate hikes of up to 60 percent for next year.
In Illinois, major insurer Blue Cross Blue Shield is asking for rate hikes between 23 and 45 percent higher next year.
In New York, insurers are asking for average rate hikes of 16.6 percent.
However, Pearson said, that while "in certain regions they [premium hikes] will be really high ... the national average will be somewhat modest."
"They'll sit somewhere around 10 percent," Pearson said.