Medicaid enrollment changes following the ACA

Medicaid and the Affordable Care Act

The Patient Protection and Affordable Care Act (ACA, P.L. 111-148, as amended) establishes new avenues to coverage for low- and moderate-income individuals. As enacted, the law required states to extend Medicaid eligibility to adults with incomes below 138 percent of the federal poverty level (FPL), although the June 2012 Supreme Court ruling in National Federation of Independent Business v. Sebelius effectively made the expansion optional for states. For more information, see Medicaid expansion to the new adult group.

Recent data suggest that Medicaid and CHIP enrollment has increased following implementation of the ACA, while the rate of individuals without insurance has declined (Berchick et al. 2018). For more information, see Changes in coverage and access.

Medicaid enrollment changes nationally

Overall, as of July 2018:

  • 73 million individuals are enrolled in Medicaid or CHIP, and
  • enrollment increased by 15.6 million among the 49 states reporting both baseline (July–September 2013) and July 2018 data.[1]

This represents a 27.5 percent increase over the baseline (CMS 2018).

Medicaid enrollment increases in expansion states

States that expanded Medicaid to cover the new adult group showed the largest growth in enrollment. Between July and September 2013 and July 2018:

  • enrollment in Medicaid expansion states increased by 13.6 million or 35.9 percent;
  • 21 of these states saw increases in enrollment of at least 25 percent; and
  • increases ranged from 0.4 percent in Vermont to 104.6 percent in Kentucky (CMS 2018).

Recent growth in Medicaid enrollment has been driven primarily by adults qualifying under the adult group (MACPAC 2016). As of December 2016:

  • Enrollment in the new adult group made up 20.4 percent of Medicaid enrollment across all reporting states (CMS 2017).[2]
  • At that time, the 31 expansion states and the District of Columbia reported a total of 14.9 million enrollees in the new group. Of these, 80.2 percent were newly eligible individuals and entitled to the 100 percent federal matching rate (CMS 2017).[3]

Increased enrollment among previously eligible individuals

Medicaid enrollment has grown regardless of expansion status in all but two states, Nebraska and Wyoming, following implementation of the ACA. This is likely due to the so-called woodwork or welcome-mat effect in which enrollment increases among individuals who were previously eligible for coverage but not enrolled. One of the underlying reasons for the welcome-mat effect may be that previously eligible individuals may not have known they were eligible for coverage and applied as a result of increased outreach efforts surrounding ACA implementation.

In non-expansion states, growth in Medicaid enrollment was lower than in Medicaid expansion states. Between July and September 2013 and November 2017:

  • enrollment increased by 1.9 million or 10.2 percent;
  • these increases ranged from 0.3 percent in Mississippi to 27.7 percent in North Carolina; and
  • three non-expansion states saw declines in enrollment: Nebraska at -0.53 percent, Oklahoma at -0.24 and Wyoming at -14.1 percent (CMS 2018).

In addition, while children’s eligibility was not affected by state decisions to expand to the new adult group, enrollment in Medicaid and CHIP has also grown among children in both expansion states and non-expansion states. As of July 2018, 35.4 million children were enrolled in Medicaid or CHIP in 48 reporting states, with child enrollment comprising more than half (50.6 percent) of enrollment in these states (CMS 2018).[4]

Alignment with projections

The Congressional Budget Office’s (CBO’s) initial projections suggested that by 2015, enrollment in Medicaid and CHIP would increase by 15 million and the number of uninsured would decline by 25 million (CBO 2010). However, following the Supreme Court ruling and the initial implementation struggles with the federal and state exchanges, CBO revised its coverage estimates under the ACA. As of March 2015, CBO estimated that 10 million additional people would be enrolled in Medicaid and 17 million fewer people would be uninsured (CBO 2015). As of July 2018, Medicaid enrollment has surpassed CBO’s revised coverage estimates, increasing by nearly 16 million from the pre-ACA baseline (CMS 2018). There were 13.3 million fewer uninsured individuals in 2017 compared to 2013 (Berchick et al. 2018).

Learn more about Medicaid enrollment:

[1] Because Connecticut and Maine did not submit enrollment data for the July–September 2013 baseline period these states are not included in the calculations depicting changes.
[2] California and North Dakota had not certified their CMS-64 submissions as of June 23, 2017. Data presented may change if states revise their data after this date. Excludes enrollment figures for the U.S. territories.
[3] Excludes U.S. territories.
[4] These data are reflective of 48 states and do not include data from Arizona, the District of Columbia, and Tennessee.