Oregon's Health CO-OP has grown its membership five-fold since last year to 10,000 members.

The growth stems from one big factor: Dr. Ralph Prows', the health plans' president and CEO, noted that much of the CO-OP's growth was driven by the popularity of its new "Select Network" plans, which cost about 4 percent to 5 percent less than broad network plans.

They were designed with an eye to lower-income consumers who make a little to much for Medicaid but qualify for federal subsidies, Prows said.

The plan's market share was relatively small to begin with — 2,000 members, much less than Moda Health's 243,000 members last year.

"We're delighted. Our mission is to serve the population that couldn't afford insurance before," Prows said.

It also doesn't hurt that the health plan dropped its rates on average by nearly 10 percent from this year, not as much as it the 21 percent cut it had requested, but still enough to allow it to undercut most of the competition, including Moda.

The CO-OP's Select Network is an option in its "Simple" and standard plans marketed to individuals in the Portland area. The tradeoff is that there are fewer providers than there are in the broad network plans.

Select Network providers are affiliated with Adventist Medical Center and Tuality Healthcare, as well as some naturopaths and specialists at Oregon Health & Science University.

Although selecting a primary care doctor is encouraged, it's not a requirement. Individuals can make specialty care appointments directly, as long as the specialists are in the network.

"We tried to get a lower cost premium but meet everyone's needs with good access and better primary care and specialty care and from the best people available," Prows said. "It's not a skimpy product."

In terms of the incentive to providers to participate, their compensation is performance-based, Prows said.

The Insurance Division reports that 81,037 people have signed up for plans through HealthCare.gov and another 62,678 outside of the federal health exchange, for 143,715 total.

That's below the 218,000 last year, but open enrollment still has another few weeks to go, closing on Feb. 15. As to whether Oregon's Health Co-OP has lured new members away from competitors such as market leader Moda Health, which had the lowest rates last year before raising premiums, that won't be known until after open enrollment closes.