Earlier this week, Aetna, which covers about 900,000 people through the health exchanges created under Obamacare, announced that it would dramatically reduce its presence those exchanges. Instead of expanding into five new states this year, as the insurer had previously planned, the company said that it would drop out of 11 of the 15 states in which it currently sells under the law.

Aetna’s decision follows similar moves from other insurers: UnitedHealth announced in April that it would cease selling plans on most exchanges. Shortly after, Humana pulled out of two states, Virginia and Alabama. More than a dozen of the nonprofit health insurance cooperatives set up under the law—health insurance carriers created using government-back loans in order to spur competition—have failed entirely. While some insurers are entering the exchanges, even more are leaving.

What this means is that in several states, and even more counties, there will be only one insurer available through Obamacare. In at least one county—Pinal County, Arizona—it is likely that there will be no insurer available on the exchange at all.