The past few years have been tumultuous for American health insurers. Barack Obama’s landmark health-care reform spawned a bevy of co-operatives to compete with them, among other measures intended to cut the cost of insurance. More than half of these have already gone bust—most recently Health Republic of New York. It had received $265m in federal loans but closed on December 1st, leaving 200,000 people in search of a new insurer. That is partly because the exchanges on which co-operatives and private insurers alike were supposed to sell lots of new policies have proved a disappointment: last month UnitedHealthcare, America’s biggest health insurer, announced that it may stop selling policies on them.