The Congressional Budget Office on Monday cut by more than a third its estimate for how many people will buy health insurance this year through government exchanges, dropping the projection to 13 million from 21 million.

In a new outlook report on the federal budget and greater economic landscape, CBO noted it earlier had projected that an average of about 15 million people would receive subsidies to discount their coverage in 2016 and that an additional 6 million people would purchase unsubsidized coverage through an exchange.

The new estimates predict that 11 million more people on average would get subsidized coverage and 2 million would buy unsubsidized coverage.

Before the CBO report was issued, federal officials had already tamped down expectations of growth in this year’s sign-up period, which ends Jan. 31. Last fall, Health and Human Services Secretary Sylvia Mathews Burwell said her agency’s goal was to have 10 million people paying for marketplace coverage by the end of 2016, up from a projected 9.1 million by the close of 2015.

The CBO noted that although it is reducing estimates for purchases through the exchanges, some people will buy insurance in other ways.

“Most of the unsubsidized people who are no longer expected to purchase insurance through an exchange are expected to purchase insurance directly from an insurer instead,” the agency said in the Monday report.

CBO estimated that about 8 million people received subsidies in 2015. Subsidies and related spending are expected to increase by $18 billion in 2016, reaching a total of $56 billion.

The report also found that for the first time, federal spending for major health care programs—Medicare, Medicaid, the Children’s Health Insurance Program, and subsidies for marketplace insurance plans—were higher than Social Security payments. Federal health spending was $936 billion in 2015, a 13 percent increase.

The projections also showed the federal budget deficit increasing in 2016 to $544 billion, or $130 billion higher than CBO projected last August. A summary of the report was issued Jan. 19.

The increase was largely attributed to legislation Congress passed in the second half of 2015, especially a tax extenders package wrapped into the year-end spending deal (PL 114-113). Federal outlays are projected to rise 6 percent, to $3.9 trillion, or about 21 percent of gross domestic product.