Enrollment in state-based marketplaces, where states do their own outreach efforts, was down by about 100,000 enrollees.
About a third of this year's enrollees (31 percent) were new enrollees, while 66 percent re-enrolled actively or automatically.
Republicans are in the midst of debating a repeal of Obamacare which would replace the current premium subsidies with less generous tax credits that would be applicable to plans beyond those offered in the ACA exchanges.
The average monthly premium for a silver plan, which most enrollees selected, went up by $84 between this year over last year. However, a vast majority of enrollees were eligible for an ACA tax credits, which on average meant that silver plan enrollees only paid a dollar more monthly than they did last year.