A recent study by Hadley and others, which used that analytic approach, examined a sample of medical claims for uninsured individuals and projected that they would receive about $28 billion in uncompensated care in 2008. That study also examined reports by doctors and hospitals and derived a higher estimate: Their gross costs of providing uncompensated care would be about $43 billion in 2008, of which $8 billion would come from doctors and $35 billion would come from hospitals. But as the study noted, at least a portion of those costs could be offset by added payments under Medicare and Medicaid to hospitals that treat a disproportionate share of low-income patients (and by similar dedicated payments made under other federal and state programs). Another recent study found that, as a group, office-based physicians roughly "broke even" when treating uninsured patients because some of those patients paid more than the doctors would have received for treating a privately insured patient.
Introduction and Background from the CBO document, Key Issues in Analyzing Major Health Insurance Proposals.