The Obama administration announced Thursday that about 12.7 million people signed up for insurance through ObamaCare this year.

The number meets the administration’s goal of between 11 million and 14.1 million sign-ups, but it is not a large increase from the 11.7 million people who signed up in 2015.

Administration officials had acknowledged from the start that this year’s sign-up period would be more difficult, given that the people most eager to join already had. They estimated in the fall that 10.5 million people were still without health insurance even though they were eligible for coverage through the ObamaCare marketplaces and that there would be a “much longer path” to signing these people up.

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Despite these difficulties preventing a dramatic increase in enrollment, officials said they were happy with the results.

Andy Slavitt, the acting administrator of the Centers for Medicare and Medicaid Services, said the sign-up period was “very successful” and showed that the ObamaCare marketplace is “strong, growing and it’s here to stay.”

Attention has fallen on the number of young people signing up, which is important to health insurers for making sure that there is the right mix of healthy and sick people (known as the risk pool) and that premiums do not need to spike too high.

The percentage of 18 to 34 year-olds in the 38 states using the federal HealthCare.gov system did not grow from last year, remaining at 28 percent of enrollees.

However, CMS officials pointed to the 4 million new enrollees this year as evidence that the sign-up pool is being refreshed. They said those new enrollees are more likely to be young and healthy, especially because many of them seemed to respond to the threat of the $695 or more penalty for lacking insurance.

“That provides great evidence that the marketplace’s risk pool is strong,” Slavitt said.

Some major insurers have recently made clear their concerns about the ObamaCare marketplaces, pointing in part to a share of sick people that is too high and contributing to losses on the marketplaces for many insurers.

Slavitt said that it is natural for insurers to have some “growing pains” in adjusting to the health law. He pointed out that before ObamaCare, insurers’ business was very different. He noted, for example, they could reject people with pre-existing conditions. Now, he said, they need to focus more on building customer loyalty and having innovative products.

He said the average consumer had over 10 insurers to choose from and “we don’t see that competition going away.”

The administration’s goal for the end of 2016 was to have 10 million people enrolled, after accounting for people who drop coverage throughout the year. Slavitt said he felt that target would be reached. The administration’s target is lower than the 13 million that the Congressional Budget Office projected would be enrolled this year.

Larry Levitt, an expert on the health law at the Kaiser Family Foundation, wrote on Twitter: “12.7 million ACA enrollees and modest growth won't quiet critics. But it's hardly a disaster they can point to on the campaign trail.”

And no matter the new numbers, there have already been record gains in lowering the uninsured rate under ObamaCare. A survey from the Centers for Disease Control and Prevention last year found that 16.3 million people had gained coverage since 2013, a number that combines gains from the law’s marketplaces and its expansion of Medicaid.

The country's uninsured rate has fallen to a record low of 9 percent since the passage of the Affordable Care Act.

This story was updated at 4:58 p.m.