"Overall, hospitals in Medicaid expansion states saw increased Medicaid discharges, increased Medicaid revenue, and decreased cost of care for the poor, while hospitals in non-expansion states saw a very small increase in Medicaid discharges, a decline in Medicaid revenue, and growth in cost of care to the poor," the report said.

Among highlights of operations in expansion state facilities:

• An operating margin increase from 2.1 percent in 2013 to 3.4 percent in 2014. Margins rose slightly in the non-expansion states.

• Charity costs fell a jaw-dropping 40 percent in expansion states, compared to 6.2 percent in non-expansion states.

• Medicaid shortfalls — the difference between what Medicaid pays and the costs of treating Medicaid patients — increased 31.9 percent between 2013 and 2014, since the hospitals were admitting more Medicaid patients.

• These shortfalls were more than offset by Medicaid revenue growth in the expansion states.

• Shortfalls grew in non-expansion states and were not offset by increased revenue.

Combining the decrease in charity care costs with the increase in Medicaid shortfalls, the net cost of caring for low income patients decreased among hospitals in expansion states, while these costs increased among hospitals in non-expansion states.

"Combining the decrease in charity care costs with the increase in Medicaid shortfalls indicates the net change in the cost to hospitals of caring for low income patients. For hospitals in Medicaid expansion states, the decrease in charity care costs ($35 million) was greater than the increase in Medicaid shortfalls ($23 million), indicating a net decrease in costs of care to the poor. For hospitals in non-expansion states, the amount of the increase in Medicaid shortfalls ($99 million) exceeded the decrease in charity care ($23 million) by a considerable amount, resulting in a large increase in the cost of care to low income patients," the report said.

The issue brief can be found here.