Affordable Care Act public exchange programs could start the year with about 6.4 million people who have already paid for 2017 exchange plan coverage or are still eligible to make payments for exchange plan coverage with a Jan. 1 effective date.

The individual major medical open enrollment period, or the time of year when people have an easy time buying 2017 coverage, started Nov. 1 and is set to end Jan. 31.

In most of the country, the deadline for buying ACA exchange plans that take effect on New Year’s Day is Dec. 15.

The Centers for Medicare & Medicaid Services says HealthCare.gov, an exchange program for states without their own exchange enrollment systems, had taken plan selection information for a total of 4.7 million people by Tuesday.

Related: HealthCare.gov attracts 246,433 new customers

ACAsignups.net, an ACA exchange tracking blog, says it’s still waiting for 2017 exchange plan enrollment activity reports from some big state-based exchanges, including the New York state and Washington state programs. But the state-based exchanges with data available by Monday were already on track to have 1.7 million effectuated, or eligible-to-effectuate, exchange plan users in their systems on Jan. 1.

ACAsignups has estimated that all ACA exchange programs combined could end up with about 13.8 million people signing up for 2017 coverage by Jan. 31.

Consumers have to make at least one exchange plan premium payment to put new coverage into effect. In the past, consumers who have picked ACA exchange plans have effectuated about 85 percent to 90 percent of the policies selected, according to exchange program data.

Florida, which has been the biggest HealthCare.gov market since the ACA exchange system came to life in January 2014, accounted for about 878,000, or 22 percent, of the 4 million people who signed up for exchange coverage through HealthCare.gov by Saturday.

Covered California, California’s state-based exchange, says it had attracted 153,000 new plan selectors as of Tuesday, up from 144,000 a year earlier. The exchange also has about 1.2 million current users. It expects a majority of those users to start the year still using the plans it distributes.

Enrollment totals could rise significantly by the end of the week. In the past, exchange enrollment activity has surged around enrollment deadlines.

Covered California managers say they will accommodate last-minute shoppers by pushing their program’s enrollment deadline for Jan. 1 coverage back to Saturday.

Web-based supermarkets

Drafters of the Affordable Care Act created the exchange system, or the family of web-based health insurance supermarkets, in an effort to hold down the cost of individual health coverage by increasing sales. Consumers are supposed to be able to use the exchange websites to compare plans on an apples-to-apples basis.

The open enrollment period for 2017 is the fourth under the ACA system.

Regulators, insurers and exchange managers developed the open enrollment period to try to keep consumers from seeing the ACA ban on traditional medical underwriting as an invitation to pay premiums for coverage only when they are sick.

For exchange program managers, one challenge has been issuer frustration with exchange plan program losses and CMS ACA program administration decisions.

Many large insurers reduced their participation in the exchange system, and reduced agent and broker commissions on the 2017 exchange plans they are selling.

Another challenge has been issuer, broker and consumer uncertainty about how the new political situation in Washington might affect the ACA exchange system.

Related:

ACA exchanges report strong early application activity

Net ACA exchange plan premiums may fall for many

Are you following us on Facebook?