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As the 115th U.S. Congress deliberates the future of the Affordable Care Act, an interactive map from the Kaiser Family Foundation provides estimates of the number of people in each congressional district who enrolled in a 2016 ACA marketplace health plan and the political party of each district’s representative as of January.

The analysis also includes maps charting the total number of people enrolled under the ACA Medicaid expansion in 2015 in states that implemented the ACA Medicaid expansion, along with the political parties of their governors and U.S. senators. As of January 2017, among states that adopted the Medicaid expansion, 16 have Republican governors, 14 have Democratic governors, and one has an Independent governor. In Washington, D.C., which also expanded Medicaid, the mayor is a Democrat.

The map below shows estimates of ACA Marketplace enrollment as of March 2016 by congressional district, with red and blue districts representing those with a Republican or Democratic congressional representative.  Districts with darker shading have a greater number of Marketplace enrollees.  Of the 11.5 million Marketplace enrollees nationally, 6.3 million live in Republican districts and 5.2 million live in Democratic districts. Marketplace enrollees per Republican district range from 10,200 enrollees in West Virginia’s District 3 to 96,300 enrollees in Florida’s District 27, with a median of 24,300 enrollees per district. Marketplace enrollees per Democratic district range from 5,200 enrollees in Hawaii’s District 1 to 94,100 enrollees in Florida’s District 10, with a median of 23,600 enrollees per district. The ten congressional districts with the highest number of Marketplace enrollees are all in Florida. There are 17 congressional districts (8 Republican districts and 9 Democratic districts) with over 50,000 enrollees, located in the following states: Florida, North Carolina, Georgia, and Montana.

As of January 2017, 32 states including the District of Columbia implemented the ACA Medicaid expansion to adults. This expansion extended Medicaid eligibility to many adults who were previously excluded from Medicaid. In 2015, about 14 million Medicaid enrollees were adults in the expansion group. This group includes those who were made newly eligible by the ACA Medicaid expansion as well as a smaller group of enrollees who were eligible for Medicaid through pre-ACA eligibility pathways (see methods for more details). The expansion group accounts for 18% of all Medicaid enrollees. Since 2015, this number has likely grown as enrollment has continued to increase and additional states have expanded, including Louisiana and Montana.


The map below shows the number of people enrolled in each state’s Marketplace (as of March 2016) and through the Medicaid expansion (as of December 2015). The map also shows the number of enrollees with advanced premium tax credits in each state, the estimated total annual premium tax credits received by enrollees in state marketplaces, and the number of enrollees with cost sharing reductions in each state (as of March 2016). States are color-coded by the U.S. Senators’ party affiliation with red states representing those with two Republican senators, blue states being those with two Democratic senators, and purple states having a mix of Republican and Democratic senators. As of March 2016, 4.0 million Marketplace enrollees live in red states, 4.4 million live in blue states, and 3.2 million live in purple states. In 2015, about 1.3 million Medicaid expansion enrollees lived in red states, 10.4 million lived in blue states, and 2.3 million lived in purple states. (Washington, DC does not have a senator, so its 62,000 enrollees are not included in these totals).




Marketplace enrollment by congressional district as of March 2016 is estimated using county-level plan selection data (from ASPE for Healthcare.gov states, and from state reports for State-Based Marketplaces). Because not all people who selected a Marketplace plan paid their premium and effectuated their coverage, adjustments were made to match each state’s effectuated enrollment totals. For Minnesota and New York, Basic Health Plan (BHP) enrollment is also included. A county/congressional district crosswalk was created using data from Missouri Census Data Center and state reports for the three states that have been redistricted (VA, NC, and FL). For counties that cross congressional district boundaries, enrollment was proportionally assigned based on the percent of the county population living in each congressional district. Enrollment is rounded to the nearest 100. Medicaid enrollment is from both the Medicaid Budget and Expenditure System (MBES) and the California Department of Health Care Services report is reported for each month. In an effort to take into account that some beneficiaries are enrolled for only part of the year, maximum monthly enrollment for each state is used to estimate total annual enrollment. Enrollment is rounded to the nearest 100. States totals may not sum to national total due to rounding. Expansion Group Enrollment: Total number of adults who have enrolled in Medicaid as a result of the ACA expansion of the program. This includes those made newly eligible for Medicaid by the ACA Medicaid expansion and some enrollees in the expansion group who were eligible for Medicaid through pre-ACA eligibility pathways. The not newly eligible enrollees group includes some childless adults in early expansion states as well as those who may be subject to technical adjustments. Some states already provided coverage at the traditional match rate to parents and adults without dependent children up to at least 100% FPL statewide as of March 23, 2010, when the ACA was enacted. The law provides additional federal funding to these states through the “expansion state match rate” for adults without dependent children under age 65; this “expansion state match rate” is higher than the traditional match rate. In addition, a few states were able to make adjustments to account for individuals who would not have been eligible because of asset test requirements in place on December 1, 2009, enrollment caps in effect for waiver populations receiving full benefits as of December 1, 2009, and other special circumstances. These adjustments may result in some adults being enrolled in the expansion category who do not qualify for the 100% federal match for newly eligible adults. Louisiana and Montana expanded Medicaid after December 31, 2015 so no data is available (Montana on 1/1/16 and Louisiana on 7/1/16). North Dakota has not submitted data to CMS.

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