As the open enrollment period for Obamacare’s health insurance exchanges comes to a close at the end of this month, grumblings from insurers indicate that part of the healthcare law is collapsing under the weight of the administration’s desire to sign up as many people as possible, even if it means insurers lose money on the deal.

UnitedHealth, the nation’s largest insurer, recently announced it expects to lose more than $500 million on the Obamacare exchanges this year — after losing $475 million last year. In November, the insurer said because of higher-than-expected cost claims it was considering pulling out of the exchanges altogether in 2017.