A study published in the American Journal of Public Health found that 67 percent of people filing for bankruptcy were wiped out by medical bills. That amounts to 530,000 families per year, a "figure that is virtually unchanged since before the passage of the Affordable Care Act (ACA)."

From Physicians for a National Health Program:

Dr. David Himmelstein, the lead author of the study, a Distinguished Professor at the City University of New York's (CUNY) Hunter College and Lecturer at Harvard Medical School commented: "Unless you're Bill Gates, you're just one serious illness away from bankruptcy. For middle-class Americans, health insurance offers little protection. Most of us have policies with so many loopholes, copayments and deductibles that illness can put you in the poorhouse. And even the best job-based health insurance often vanishes when prolonged illness causes job loss – just when families need it most. Private health insurance is a defective product, akin to an umbrella that melts in the rain."

In the article, the authors note that "medical bills frequently cause financial hardship, and the U.S. Consumer Financial Protection Bureau reported that they were by far the most common cause of unpaid bills sent to collection agencies in 2014, accounting for more than half of all such debts."