The number of paying Obamacare customers was just under 10 million by June 2017 — about 2.3 million fewer than the number that selected an Obamacare health plan during open enrollment earlier in the year.
The level of drop-off between people who sign up for Obamacare coverage and those who pay their plan's first month of premiums was similar to that seen in 2016, according to data released Wednesday.
There are a variety of reasons why a person who selected a plan would not end up paying, including finding coverage elsewhere, or being unable to afford their plan.
In June, 9.9 million individuals continued to have Obamacare coverage, compared with 12.2 million who had selected a plan sold on a government-run marketplace, the Centers for Medicare and Medicaid Services said.
That represents a decrease of nearly 19 percentage points.
Last year, 12.7 million people selected a health plan offered during open enrollment on a government marketplace. Enrollment ended in early 2016 for plans in effect that same year.
By June 2016, there were 10.4 million paying customers in those plans, a drop-off of slightly more than 18 percentage points.
Enrollment in Obamacare plans is only considered to be official, or "effectuated," when a customer pays their first month of premiums.
The new report about effectuated enrollment was released minutes before CMS issued an updated tally of the number of people who have selected an Obamacare plan for 2018 coverage from the federally run marketplace HealthCare.gov.
So far this enrollment season, which began Nov. 1, a total of almost 4.7 million people have chosen a HealthCare.gov plan.
While that is higher than the number of people who had selected such a plan at the same point last year, the final national tally for Obamacare enrollment for 2018 plans is likely to fall short of this past year's total of 12.2 million.
The last open enrollment season ran through the end of January.
But this season, the deadline for signing up for coverage is Friday for HealthCare.gov, which serves 39 states. Most of the other states that run their own Obamacare marketplaces have later deadlines.
The pace of sign-ups on HealthCare.gov would have to accelerate considerably this week to match last year's final enrollment levels.