The Obama administration announced Thursday that a little more than eight million Americans have signed up for private health care coverage in state and federal marketplaces created under the Affordable Care Act (ACA) during its first enrollment period which ended on April 19. An additional five million individuals purchased plans outside of the marketplaces that comply with ACA standards. As a result, the White House, in an attempt to respond to critics who warn that premiums will soon skyrocket, predicts that the costs for the consumers will not increase significantly over the next year.

The administration based its prediction of stable costs on the number and demographics of those who bought plans through the marketplaces as well as through private companies providing ACA-compliant plans. Both sets of plans purchased in any given state are considered in one overall risk pool. The risk pool consists of the spectrum of customers ranging from young and healthy to old and diseased. The risk pool currently numbers at 13 million, and the administration anticipates the present are enough younger, healthier, lower-cost participants to balance the higher-cost customers for a net result of stable premiums.

“We believe, based on the data that we’ve seen and independent data that’s out there, that premiums will be stable and that the risk pool is sufficiently large and varied to support that kind of pricing in every state,” said Mike Hash, Department of Health and Human Services.

Among all Obamacare marketplace customers, 85% applied for federal subsidies to help offset their premiums. The marketplace plans were available in three tiers, Gold, Silver, and Bronze, ranging from extensive to basic coverage, respectively. Approximately 67% of enrollees selected Silver plans, and twenty precent chose Bronze plans, meaning only about ten percent enrolled in Gold plans, the best coverage offered by the ACA marketplaces.

With midterm elections approaching and key congressional seats on the line, Obamacare premiums are in the political spotlight. Earlier in the week, Republican members of the House Energy and Commerce Committee released a report showing that only about two thirds of those who signed up have actually paid their premiums. However, the Democrats and White House officials claim the study findings are inaccurate.

Earlier last month, the White House released its ACA Fact Sheet summarizing a number of key metrics for Obamacare. Among these, one of the most important changes brought by the ACA is the elimination of pre-existing conditions exclusions. Almost 130 million Americans no longer face premium increases or denials of coverage because of pre-existing conditions. Over 100 million will no longer lose coverage after reaching a lifetime limit.