When President Obama described the Affordable Care Act’s health-insurance exchanges in late 2013, he declared they would create “more choice, more competition, [and] real health-care security” for millions of Americans. This hasn’t panned out. Nearly three years later, choice and competition have declined, a problem that is already set to worsen in 2017.

UnitedHealth Group is the latest proof. On April 19, the company announced that it will abandon the exchanges in all but a “handful” of the 34 states in which it currently operates. This could leave up to 6 percent of the Affordable Care Act’s subscribers scrambling for new plans before year’s end.