Washington Post:

“Enrollment is key, first and foremost,” said Sara R. Collins, a vice president at the Commonwealth Fund, a nonpartisan foundation that funds health-care research. “They have to have this critical mass of people so that, by the law of averages, you’re going to get a mix of healthy and less healthy people.”

A big reason the CBO projections were so far off is that the agency overestimated how many people would lose insurance through their employers, which would force them into the exchanges. But there have been challenges getting the uninsured to sign up, too.

The law requires every American to get health coverage or pay a penalty, but the penalty hasn’t been high enough to persuade many Americans to buy into the health plans. Even those who qualify for subsidized premiums sometimes balk at the high deductibles on some plans.

And people who do outreach to the uninsured say the enrollment process itself has been more complex and confusing than Obama’s initial comparison to buying a plane ticket.

“This exchange will allow you to one-stop shop for a health-care plan, compare benefits and prices, and choose a plan that’s best for you and your family,” Obama said in a speech in 2009. “You will have your choice of a number of plans that offer a few different packages, but every plan would offer an affordable, basic package.”

In some markets, a shortfall in enrollment is testing insurers’ ability to balance the medical claims they pay out with income from premiums. In an announcement curtailing its involvement in the exchanges this month, Aetna cited financial losses traced to too many sick people signing up for care and not enough healthy ones.

The health-care law has been a political lightning rod from the beginning, and Republican legislators have used insurance companies’ withdrawals from the exchanges to reignite calls for the law’s repeal.