CLOSE Five states are expected to have just one company selling insurance on the 2017 Obamacare exchanges and consumers in most of the counties in nine other states won't find any competition for their exchange business either. Martin E. Klimek, USA TODAY

Leah Sondergeld of Mesa,, Ariz., will have to change her ACA exchange plan for the third time this fall for her daughter Kate, 25, who has epilepsy with myoclonus. Kate is back at college after taking a year off to deal with the diagnosis last year. (Photo: Nick Oza, Arizona Republic)

Up to 2.1 million people will likely have to change plans for 2017 due to insurers leaving states' Affordable Care Act marketplaces, up from more than 1.2 million who had to find new insurers last year. That doesn't include the millions who bought new plans because they found a better deal.

The new estimates, from data expert Charles Gaba of ACASignups.net, come as another analysis shows five states are expected to have just one company selling insurance on the 2017 Obamacare exchanges. Consumers in most counties in nine other states won't find any competition for their exchange business either, according to the Kaiser Family Foundation.

These latest assessments show how leery insurers are of the costs and rules associated with selling on the ACA exchanges — the centerpiece of the health law — and the risks this reticence present to their future. Insurers including Aetna, UnitedHealthcare and many smaller insurers and cooperatives have either decided to leave states and counties or have failed. Julie McPeak, who was appointed insurance commissioner by the Republican governor, told The Tennessean that the ACA marketplace for the state was "very near collapse."

The turmoil is putting intense pressure on federal regulators to stabilize the system, lower costs for consumers and reduce risks for insurers — often conflicting challenges that create a Catch-22. Among other changes, the Centers for Medicare and Medicaid Services proposed Monday to have its risk adjustment program factor in prescription drug usage data and the people who drop their coverage before 12 months are up. Insurers complain too many sick people sign up to get health care and then drop plans after their treatments are complete.

Insurers need healthy people to buy insurance to offset the companies' costs of covering sicker ones, but healthy consumers who don't qualify for high subsidies won't sign up unless the prices are more affordable, says Paul Howard, director of health policy at the free market Manhattan Institute.

"It's important that enrollment continue to grow," so the ACA sign-up period that starts Nov. 1 will be critical, says Kaiser Family Foundation vice president Gary Claxton. Regulators also need to "work with industry to figure out what issues remain and what to do about them."

Although the health law hasn't become the hot button issue it was in the last presidential election, the Obama administration still must make changes against a backdrop of fierce partisan opposition to Obama's signature law. That means no one expects solutions requiring congressional action before the November elections.

Kevin Counihan, CEO of Healthcare.gov which handles Obamacare sales for 38 states, says insurers are adjusting at different rates to the exchanges. (Photo: Jayne O'Donnell, USA TODAY)

"This is probably the most frustrating public policy dilemma we've got right now in the country," says Wayne Goodwin, North Carolina's Democratic insurance commissioner. "Businesses and health insurance companies have invested so much into the ACA, there is a tremendous urgency to having Congress and whoever the new president is fix the law."

South Carolina and Alabama are grappling with what will likely be no competition for the first time in 2017 after insurers Aetna and United Healthcare announced plans to leave the whole states. And the Kaiser's analysis shows 31% of counties will likely have just one insurer in 2017 and another 31% are expected to have only two.

Kevin Counihan, CEO of Healthcare.gov, which handles the exchange sales for 38 states, emphasizes that insurers are adjusting at different rates to selling on the exchanges.

"With high consumer satisfaction, more people getting care, and an improving risk pool, incoming data continue to show that the future of the Marketplace is strong." he said after Aetna's announcement this month that it would stop selling on the exchanges for 11 states.

CMS also often notes that rate increases haven't been as "high as people were expecting, but it doesn't matter because people aren't buying" plans unless they are heavily subsidized, says Howard of the Manhattan Institute.

Arizona is facing one of the country's most dramatic swings in insurance company participation on the ACA exchange with 80% of the counties served by just one insurer. Pinal County, Arizona's third most populous, is the only county in the United States currently without an insurer selling on the exchange for 2017.

Six insurers that sell plans directly to consumers are bowing out or scaling back on the Affordable Care Act marketplace in Arizona