In Windsor Heights, Iowa, 35-year-old Geoffrey Wood, the chief operating officer of Startup Genome, said he signed on for the state’s co-op, CoOportunity Health, because he had grown tired of dealing with his previous insurer, Aetna Inc.’s subsidiary Coventry Health Care Inc.

‘New Guy’

“Given the choice between them, as the incumbent company, and an innovative company trying to do something different, I didn’t feel like I had much choice,” Wood said in a telephone interview. “I decided to give the new guy a shot.”

Cynthia Michener, an spokeswoman for Hartford, Connecticut- based Aetna, said Coventry’s advantages for enrollees include experience with the Iowa health-care system and stability. She declined to discuss Wood’s case without authorization from him.

“Coventry Health Care has served Iowans for more than two decades, and knows the community and its health-care needs well,” Michener said in an e-mail. “We have long-standing experience of providing health insurance and benefits and helping members access care, and a track record of financial stability to pay claims.”

About 4 million Americans have signed up for private health plans using new marketplaces created by the law, the U.S. government says. The Congressional Budget Office projects 6 million will enroll this year, a reduction of 1 million from estimates before the troubled introduction of the law began in October.

Slow Starts

It hasn’t been a smooth road for some of the co-ops. The computer bugs and errors that prevented many Americans from signing up for coverage in October and November took a toll and, in some states, the startups continue to struggle.

Co-ops in Maryland, Oregon and Massachusetts, for instance, haven’t hit their target enrollments because their state-run exchanges still aren’t functioning well. And Vermont’s co-op dissolved in September, returning its federal solvency loans, after state regulators denied it an insurance license, saying the company’s enrollment expectations were unrealistic and its proposed rates weren’t competitive.

“They’re finding their way to us off the exchange, fortunately,” Dawn Bonder, CEO of Oregon’s Health Republic Insurance, one of two co-ops in the state, said in a phone interview. She estimated the company signed up about 4 percent to 5 percent of customers using Oregon’s exchange, which had enrolled about 33,800 people by February, according to the U.S. government.