More rural regions than ever before will have only one insurer’s plans available to customers in the Affordable Care Act’s marketplaces for 2017, reported the Wall Street Journal.

According to data from the Kaiser Family Foundation tracking the exit of insurers from exchanges—like UnitedHealth and Humana—at least 650 counties are set to have only one insurer to choose from in 2017, up from 225 in 2016. Cynthia Cox, a researcher at the foundation, told the WSJ that around 455 of those counties would be considered rural.

Exchanges in Alabama, Alaska and Wyoming are set to have one insurer’s plans available statewide, according to state regulators, along with parts of Arizona, Kentucky, Mississippi, Oklahoma and Tennessee. It’s possible the number of single-insurer counties could change, because companies don’t have to finalize their approaches with regulators until September.

The departure from rural areas can largely be blamed on the cost for insurers to cover people in those parts of the country. An analysis by health technology firm Inovalon found monthly costs per plan member for insurers were significantly higher in smaller towns and cities. The average monthly cost for an individual living in a town with a population of between 2,500 and 10,000 was nearly $570, compared to $415 per month for a member living in a city of 50,000 people or more.

The limited choices for 2017 are a cause for concern for regulators.

“When there’s more competition, consumers typically are better off,” Mark Fowler, chief of staff at the Alabama Department of Insurance, told the WSJ.

Fowler confirmed Humana and UnitedHealth will be exiting the state’s marketplace in 2017, leaving only plans from Blue Cross and Blue Shield of Alabama.