This is an archived article that was published on in 2014, and information in the article may be outdated. It is provided only for personal research purposes and may not be reprinted.

Washington • The number of Utahns who picked a plan through a federal health exchange went up tenfold in the past month, part of a spike seen around the nation that puts the Affordable Care Act on stronger footing, but still behind early enrollment expectations.

Nationwide, nearly 2.2 million Americans had selected a plan through a federal or a state-based exchange by Dec. 28, though some of them haven't taken the final step and paid their first premiums. In Utah, 18,633 have picked a plan through the federally run exchange — compared with just 1,865 a month ago.

And new details show that roughly a fourth of those signing up are under age 35, the key demographic needed to ensure that premiums don't surge in the future.

"We are pleased to see such a strong response and a heavy demand for the health-insurance marketplace," said Kathleen Sebelius, secretary for Health and Human Services (HHS), who announced the numbers Monday.

The federal government hopes to sign up 7 million people in private plans before open enrollment ends March 31. An earlier HHS projection showed the administration wanted to reach 3.3 million nationwide and 26,790 in Utah by the end of 2013.

Hitting those early goals was made far more difficult with the disastrous rollout of the site. Not only were people unable to sign up for plans early on, but the administration also had to shelve its public-relations push because there was no reason to encourage someone to visit a site that wasn't functioning properly.

The site is now working for the majority of users, and the administration is "in the middle of a sustained outreach effort" to get people to visit and sign up for coverage, said Julie Bataille, a spokeswoman with the Centers for Medicare & Medicaid Services, which is overseeing the implementation.

The Obama administration released demographic information on the sign-ups for the first time, showing that women (54 percent) and older people (56 percent over age 44) were more likely to register than men and younger people. Also, according to the data, nearly 80 percent of those who did pick a private plan received federal subsidies that helped lower monthly costs.

Supporters and opponents of the law dubbed Obamacare have targeted young Americans because they are likely to be healthier than the rest of the population. If they sign up in significant numbers, it will create a healthy risk pool; if they don't, it could result in a spike in prices for insurance.

HHS officials say the sign-ups tracked their expectations so far, where nationwide 24 percent of people who picked a plan are between ages 18 and 34. In Utah, which has one of the nation's youngest populations, 18- to 34-year-olds made up 29 percent of the pool.

Young Americans are the most likely to be uninsured. Out of the 380,000 Utahns who didn't have coverage last fall, the Utah Department of Health estimated that 46 percent of them were 18 to 34 years old.

"We expected older adults to sign up early, and we expect more young adults to come in in the month of March — by the end of the open-enrollment period is what I should say," said Nancy Delew, an HHS planning official.

Department officials say they are confident they will have "an appropriate mix of individuals enrolled."

The new data show that 67,000 Utahns applied for coverage through and nearly 43,500 were eligible for insurance.

Of those people, almost 28,000 would get federal assistance paying for premiums, meaning that 15,500 would have to pay the premiums on their own because of their income.

Of the almost 28,000 eligible, 18,633 actually selected a plan. HHS released no information on how many of these people were uninsured.

Beyond those picking private insurance plans, nearly 1.6 million people nationwide and 20,543 Utahns have been determined to be eligible for Medicaid or the Children's Health Insurance Program when they signed up on the exchanges.

Twitter: @mattcanham