That's a problem because the success of the Affordable Care Act hinges on signing up enough "young invincibles," who would need less care, in order to pay for the sick and elderly. The White House was banking on 40% of signups being aged 34 or less.
If the numbers don't balance out as needed, premiums could rise. Moreover, health insurers have until May to decide whether they will keep providing exchange plans in 2015.
Around 2.2M people bought coverage in the three months through December, 79% of whom received a discount due to federal subsidies.