The Medicaid expansion has been particularly successful at covering uninsured adults. According to new research in Health Affairs that used data from the Health Reform Monitoring Survey, expansion states saw a decrease in their rate of uninsured adults from about 16% during the third quarter of 2013 to 7% in the first quarter of 2017. During the same time period, the rate of uninsured adults in states that did not expand Medicaid dropped from 20% to 15%.

Among adults at or below 138% FPL, the uninsurance rate declined over 40%– from almost 40% in the third quarter of 2013 to about 22% in the first quarter of 2017. Most of these gains were due to Medicaid. When the authors compared rates of uninsurance for adults at or below 138% FPL, they found that the rate was almost 2.5 times higher in non-expansion states compared to expansion states. When the authors looked at the insurance gains by age, they found that the largest gains were among adults ages 18-34 and 50-64, and the driving source of the gain in coverage was Medicaid.

We know that Medicaid drove down the rate of uninsured adults, but how about the cost of insuring the newly eligible adult population? Another recent study in Health Affairs found that newly eligible Medicaid enrollees ages 19-64 spend less and use less care than the previously eligible Medicaid adults ages 19-64 (the authors exclude previously eligible Medicaid adults who had a disability or were pregnant). Average monthly expenditures for newly eligible enrollees were more than 20% less than average monthly expenditures for previously eligible enrollees: $180 compared to $228. Newly eligible enrollees spent significantly less on prescription drugs, office visits, outpatient hospitalizations and emergency department visits.

And if you need a refresher on the number of adults enrolled in Medicaid who are newly eligible, you can find every state’s data here as of September 2016.