We used data from the Medical Expenditure Panel Survey–Household Component to examine coverage transitions for nonelderly US adults. We found that 71.5 percent of Marketplace enrollees in 2014 had some period of uninsurance before enrollment. In Medicaid expansion states, 17.4 percent of adults who were uninsured throughout 2013 gained Medicaid coverage in 2014, compared with only 5.6 percent in those states between 2012 and 2013.
