Final sign-ups for Obamacare plans on healthcare.gov reached 8.7 million this open enrollment, falling slightly since last week's deadline partly because some customers canceled plans they were automatically enrolled in.

A week ago, the Centers for Medicare and Medicaid Services reported that 8.8 million people signed up for plans. A CMS official told the Washington Examiner that the number declined because some customers canceled their plans within hours of the deadline, while others canceled plans they were automatically enrolled in.

Obamacare customers who do not actively change, re-enroll or cancel their plans are automatically enrolled in a new one. If they do not pay their premiums, they are not covered by the plan and risk going uninsured, and they can cancel plans they are automatically enrolled in.

The final data, which extend to Dec. 23, are difficult to parse because they include added customers who were not tallied as part of the enrollment totals released last week, including those who enrolled between midnight and 3 a.m. on Dec. 16, the final three hours on the West Coast, nor did they include people who had left their numbers with a call center and would still be allowed to enroll. The latest data from Thursday include a mix of these as well as those who dropped out of plans.

Customers are not considered fully enrolled in plans until they pay their first months of premiums. Other states that have their own exchanges are still holding open enrollment periods, and some customers can still change their plans under special enrollment provisions.

Healthcare.gov is the exchange that most states use for customers who can enroll in private coverage that is subsidized by the federal government. Last year, when open enrollment lasted three months rather than six weeks, final enrollment was slightly higher, at 9.2 million people.

This was the first open enrollment under President Trump, and Democrats and pro-Obamacare advocates have accused the administration of intentionally trying to suppress enrollment through actions from health officials in charge of carrying out the signup period. The administration cut funding for navigators who help people sign up for coverage, saying they had failed to effectively get people enrolled, and cut 90 percent of funding for advertising enrollment. It also cut the open enrollment period in half.

A week after the Dec. 15 deadline for open enrollment, Trump signed a tax code overhaul bill into law that repealed the Obamacare penalties associated with the individual mandate, which required people to buy health insurance or pay a fine. It's not clear whether that had an impact on the drop in enrollment.