Over the last decade, medical bills have become the largest source of debt that Americans owe collection agencies, according to new research co-authored by Associate Professor of Public Policy Wesley Yin. The $140 billion in unpaid health care bills, held by about 18% of Americans, now exceeds all other debt in collections combined, according to the paper just published in the Journal of the American Medical Association (JAMA). Only debts referred to collection agencies were measured; other unpaid bills owed to health-care providers would push the total amount of debt even higher. Yin and co-authors Raymond Kluender of Harvard Business School, Neale Mahoney of Stanford University and Francis Wong of the National Bureau of Economic Research examined records from the credit rating agency TransUnion from January 2009 to June 2020, reflecting medical care delivered prior to the COVID-19 pandemic. Their comprehensive look at the evolution of medical debt reveals that, while Americans’ household finances largely recovered after the Great Recession, medical debt continued to grow. Yin said the debt was most concentrated in low-income communities and in the South. He added that, in 12 states that chose not to expand Medicaid coverage, significant disparities grew even worse during the period studied. “Addressing the problem of medical debt in the U.S. health care system must be a high priority,” said the authors of a JAMA editorial accompanying the study. “In addition to the potential consequences for health and health care use, the economic and social ramifications of medical debt are likely equally consequential, if not more so.”