Obama administration officials on Thursday predicted health insurance premiums would be stable next year despite concerns that not enough young and healthy people signed up through the online insurance exchanges. "The risk pool is fundamentally large and varied to support that kind of pricing…in every state," said Mike Hash, director of the office of health reform for the Health and Human Services Department. "We believe … premiums will be stable." The upbeat assessment came as the administration offered the broadest glimpse yet of the demographics of the 8 million Americans who enrolled in health insurance through the health law's online marketplaces through mid-April. Open enrollment for this year has ended in nearly all states and will re-open in November.