"Despite low premiums offered by Medicaid insurers, Blue Cross Blue Shield insurers accounted for almost half of marketplace enrollment nationally in 2018," the report states, noting that BCBS affiliates are responsible for the majority of marketplace enrollments in 11 states.

The states where BCBS insurers hold nearly all marketplace enrollment include Alaska, Alabama, Delaware, Illinois, Louisiana, North Carolina, North Dakota, New Hampshire, Oklahoma, South Carolina and Wyoming.

Erik Wengle, research analyst for the Urban Institute and one of the authors of the report, said that in a lot of areas around the country, Blue Cross-affiliated insurers are the only participating insurers, particularly for rural areas.

"This has changed somewhat in recent years and is likely to change more in the future as more insurers enter the marketplaces," Wengle said. "However, these were the dominant insurers in the individual market in many places around the country and have strong brand recognition, and likely broad provider networks, making an attractive option for consumers."

BCBS insurers have also cornered the majority of the enrollment market in nine other states—Arkansas, Florida, Hawaii, Kansas, Michigan, New Jersey, Pennsylvania, Tennessee, West Virginia—but Medicaid insurers are gaining on their share of the market in those parts of the country, according to the report.

Still, the brief shows that Medicaid insurers dominate in Arizona, Georgia, Kentucky, Indiana, Mississippi, New Mexico, Ohio and Texas.

The data reveals that regional and national insurers remain the top enroller of marketplace consumers in six states. "We find that there are six states with national/regional insurers enrolling most of the market's consumers," according to the findings. "Many of the largest national insurers (Aetna, UnitedHealthcare, Humana) have left nongroup marketplaces throughout the country, but this type of insurer, along with regional insurers, remains important in some states."

The researchers offered a critical caveat to the report on the Robert Wood Foundation website. The data had been gathered prior to COVID-19's influence on economic outcomes. "The Marketplace enrollment is expected to increase due to wide-scale unemployment and the loss of employer-sponsored insurance from the COVID-19 crisis and associated economic fallout," the website notes.

Given the dearth of information at this point, Wengle said he can't predict with certainty what will happen.

"Consumers are likely to be price sensitive given their reduced income, but beyond that we cannot say unfortunately," he said.

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