While the final figures will be somewhat different once the more complete end of year data is available, at this point it is reasonable to expect that for the three-year period of 2014 through 2016, the net increase in health insurance enrollment was 16.5 million individuals. Of that figure, 13.8 million were added to Medicaid and 2.7 million were the net increase in private-sector coverage enrollment.

In general, enrollment data indicate that the implementation of the ACA appears to have had three effects on health insurance coverage: (1) a substantial increase in individual-market enrollment; (2) an offsetting decline in fully insured employer-group plan enrollment; and (3) a significant increase in Medicaid enrollment in states that adopted the ACA Medicaid expansion.

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