O-Care enrollment steady in Calif.

Enrollment under California's ObamaCare insurance exchange has continued steadily into January despite expectations that it would decline after the end of last year.

The marketplace, known as Covered California, reported Tuesday that roughly 125,000 people signed up for private coverage between Dec. 31 and Jan. 15.

The figure reflects a sustained rate of activity on one of ObamaCare's most successful state-based marketplaces.

California's system has now registered approximately 625,000 people for private health plans since October. By comparison, the federal system serving 36 states had enrolled about 1.1 million people by the end of December.

"We’re encouraged by the outpouring of interest and participation in the state insurance exchange," said Covered California Executive Director Peter V. Lee in a statement.

"These impressive numbers for the first half of open enrollment and the continued momentum in January tell us we are on track to meeting, if not beating, those enrollment estimates as we continue to pick up steam."

Analysts had predicted the enrollment in states like California would lose momentum after ObamaCare's first big deadline — to buy coverage that began Jan. 1 — had passed at the end of December.

Tuesday's figures suggest that at least in some areas of the country, sign-ups are continuing apace as insurers and the federal government launch ad campaigns designed to market ObamaCare coverage to the uninsured.

California announced that as of Dec. 31, about 25 percent of its enrollees in private plans were younger people between the ages of 18 to 34.

While this matches results seen around the country, some experts caution that unless younger people represent at least 40 percent of the risk pool, the marketplaces will see higher prices next year.