In addition to the Medicaid expansion, The Patient Protection and Affordable Care Act (ACA, P.L. 111-148, as amended) established premium subsidies for the purchase of private coverage on the exchanges for those with incomes between 100 percent and 400 percent of the federal poverty level. Together with other changes to the insurance market, these new coverage options were intended to increase the number of individuals with health insurance coverage (CBO 2010). It also was anticipated that gains in health coverage would lead to improved access to and use of services.
Enrollment data provide only one data point; to understand the broader impact on coverage, survey data need to be examined. This is the case because the expected increase in the number of covered individuals also reflect the cumulative effect of the Medicaid expansion, other increases in Medicaid enrollment, exchange enrollment, and any new enrollment in employer-sponsored coverage. For more information, see Medicaid enrollment changes following the ACA.
Federal surveys, with their large sample sizes, provide a more complete assessment of the ACA’s impact on coverage rates, although a number of smaller, private surveys also have provided estimates on the law’s effect. Survey data released to date have shown a decline in the number of uninsured adults and a corresponding increase in Medicaid coverage. States that have expanded Medicaid have lower uninsured rates than non-expansion states. For example, according to the Current Population Survey, the uninsured rate was lower in states that expanded Medicaid (6.5 percent) than in those states that did not (12.2 percent) (Berchick et al. 2018).
While many available studies use survey data, others have used administrative data from hospitals, credit bureaus, or other sources. These studies have examined various aspects of coverage and access, including
- gains in coverage among adults and children;
- the effects of gaining coverage (either through Medicaid or in general) on unmet need, on having a usual source of care, and on utilization of particular types of health care services among low-income adults;
- the effects of using an alternative approach to expansion;
- effects of expansion on other measures of well-being, such as personal finances, psychological stress, and problems paying medical bills;
- spillover effects of increased insurance coverage on other public programs, recipients of other types of health insurance, as well as on crime.
The literature on the effects of Medicaid expansion on the goals of the ACA largely indicates that expansion was associated with increased coverage, access, quality of care, and Medicaid spending. A few studies have found negative consequences, such as increased wait times for appointments (Mazurenko et al.). Studies below are listed by date, with newer studies appearing first.
Using 2017 Current Population Survey data, the authors estimate that more than one-fourth (6.8 million) of the remaining uninsured population is eligible for Medicaid or CHIP. An additional 2.4 million uninsured individuals fall into the so-called coverage gap, meaning that they earn too much to be eligible for Medicaid, but not enough to qualify for subsidized exchange coverage. These individuals would likely be eligible for Medicaid if their states chose to expand coverage.
Benitez, J.A., E.K. Adams, and E.E. Seiber. 2017. Did health care reform help Kentucky address disparities in coverage and access to care among the poor? Health Services Research 53, no. 3: 1387–1406.
This study used 2011–2015 Behavioral Risk Factor Surveillance System (BRFSS) data to examine health disparities in Kentucky, and found that following the Medicaid expansion, high-poverty communities experienced a decrease in the share of residents who were uninsured that was 8 percentage points greater than did lower poverty areas. They also experienced a decrease in unmet need to costs that was 7.5 percentage points greater than lower poverty areas.
In this article, the authors used 2008–2015 National Health Interview Survey data to look at Medicaid expansion coverage effects. Although the uninsured rate fell in both expansion and non-expansion states between 2010 and 2015, declines were significantly greater (7.5 percentage points) in expansion states. Additionally, Medicaid expansion was associated with significantly better quality of coverage as reported by low-income adults.
Using 2013–2015 National Health Interview Survey data, this study found a link between parents gaining Medicaid eligibility and increased enrollment among children. Among children whose parents gained coverage under the Medicaid expansion, public coverage increased by 5.7 percentage points compared to 2.7 percentage points among children whose parents remained ineligible for Medicaid following the expansion (including those who remained ineligible due to their state not expanding Medicaid or for a different reason). An additional 200,000 low-income children would have gained coverage if all states had adopted the expansion.
Access to care and service use
This study used 2011–2015 data from the Uniform Data System, and found that after two years, Medicaid expansion was associated with an 11 percentage-point decrease in the share of community health center patients who were uninsured and a 13 percentage-point increase in the share of patients covered by Medicaid. For community health centers in rural areas, Medicaid expansion was associated with significant improvements in quality indicators (e.g. percentage of patients with asthma receiving appropriate treatment, adults receiving a body mass index screening, blood pressure control for patients with hypertension). For rural community health centers, Medicaid expansion was associated with a significant increase in the number of visits for 18 of the 21 visit types, versus just 4 of the 21 visit types in urban centers.
McConville, S. M. C. Raven, S.H. Sabbagh, and R.Y. Hsia. 2018. Frequent emergency department users: A statewide comparison before and after Affordable Care Act implementation. Health Affairs 37, no. 6: 881–889.
This study used data obtained from California’s Office of Statewide Health Planning and Development to look at characteristics of frequent emergency department (ED) users in California, following Medicaid expansion. It found that the odds of being a frequent ED user (i.e., of having more four annual ED visits) were significantly lower for Medicaid-insured patients. The largest predictors of frequent ED use included having a diagnosis of a mental health condition or a substance use disorder.
U.S. Government Accountability Office (GAO). 2018. Medicaid: Access to health care for low-income adults in states with and without expanded eligibility. GAO-18-607. Washington, DC: GAO. https://www.gao.gov/assets/700/694489.pdf.
Using data from the 2016 National Health Interview Survey, GAO found that low-income adults in expansion states were significantly less likely to report having unmet medical needs or financial barriers to medical and other types of health care than those in expansion states. Additionally, they were more likely to report having a usual source of health care when sick or in need of medical advice.
Biener, A., S.H. Zuvekas, and S.C. Hill. 2017. Impact of recent Medicaid expansions on office-based primary care and specialty care among the newly eligible. Health Services Research 53, no. 4: 2426-2445. October 20, 2017.
Using 2008–2014 Medical Expenditure Panel Survey data, this study found that in 2014, newly eligible adults in expansion states were 9.1 percentage points more likely to have an office-based primary care visit and 6.9 percentage points more likely to have a specialist visit, relative to their counterparts in non-expansion states.
The authors examined data from the 2014 National Health Interview Survey and 2014 Behavioral Risk Factor Surveillance System and found that following the first open enrollment period of October 2013 to March 2014, previously uninsured individuals gaining coverage through Medicaid expansions were between 47.1 and 85.6 percent more likely to report having a usual source of care.
Nikpay, S., S. Freedman, H. Levy, and T. Buchmueller. 2017. Effect of the Affordable Care Act Medicaid expansion on emergency department visits: Evidence from state-level emergency department databases. Annals of Emergency Medicine, 70 no. 2: 215–225.
The authors examined data from the Agency for Healthcare Research and Quality’s Healthcare Cost and Utilization Project’s fast stats database. They found that following Medicaid expansion in 2014 total emergency department use per 1,000 increased by an additional 2.5 visits in expansion states compared to non-expansion states. The share of emergency department visits covered by Medicaid increased by 9 percentage points and the share of emergency department visits that were uninsured decreased by 5 percentage points relative to non-expansion states.
Selden, T. M., B. J. Lipton, and S. L. Decker. 2017. Medicaid expansion and marketplace eligibility both increased coverage, with tradeoffs in access, affordability. Health Affairs 36, no. 12: 2069–2077.
This study used data from the National Health Interview Survey for 2008–2015, and found that adults with incomes between 100 and 138 percent of the federal poverty level experienced similar increases in having a usual source of care and primary care whether covered by Medicaid in expansion states or by the exchanges in non-expansion states. Although adults in expansion states experienced larger reductions in out-of-pocket spending, they also had greater difficulty accessing physicians relative to their counterparts in non-expansion states.
Holahan, J., M. Karpman, and S. Zuckerman. 2016. Health care access and affordability among low-and moderate-income insured and uninsured adults under the Affordable Care Act. April 2016. Washington, DC: Urban Institute.
Using data from the September 2015 round of the Health Reform Monitoring Survey, the authors found that individuals with Medicaid coverage were just as likely to report having a usual source of care or a recent routine checkup, but more likely to report difficulty getting a doctor’s appointment than other insured enrollees. Compared with enrollees in exchange plans, Medicaid enrollees were less likely to report unmet health needs due to affordability or problems paying medical bills.
This study used 2013–2014Medical Expenditure Panel Survey data to look at access to care among previously uninsured individuals. It found that 18 percent of individuals who were uninsured in 2013 gained coverage through Medicaid, while only 11 percent remained uninsured in 2014. In general, individuals who gained insurance coverage in 2014 experienced improved access to care, but those who remained uninsured did not.
Wherry, L. R., and S. Miller. 2016. Early coverage, access, utilization, and health effects associated with the Affordable Care Act Medicaid expansions: A quasi-experimental study. 2016. Annals of Internal Medicine 164, no. 12: 795–803.
This study used National Health Interview Survey data for 2010–2014. It found that in the second half of 2014, among adults with incomes below 138 percent, Medicaid expansions were associated with higher utilization of certain services (including those provided by general practitioners and overnight hospital stays). They were also associated with increased diagnoses for certain health conditions including diabetes and high cholesterol.
This study used data from the 2013–2015 Health Reform Monitoring Survey, and found that nationally, adults with income below 138 percent FPL were more likely to report a usual source of care as well as a routine checkup within the last year than prior to implementation of the ACA, as well as a decline in unmet need due to cost and problems paying medical bills. However, more than 20 percent reported an access problem within the past 12 months.
Garfield, R., and K. Young. 2015. How does gaining coverage affect people’s lives? Access, utilization, and financial security among newly insured adults. June 2015. Washington, DC: Kaiser Family Foundation.
The 2014 Kaiser Survey of low-income Americans and the ACA found that adults who gained coverage following the ACA were more likely to have a usual source of care, regardless of coverage type. They also were more likely to have used medical care compared to those who remained uninsured. However, newly insured adults were more likely to report difficulties finding a physician that would take them as a new patient.
Access to behavioral health and substance use disorder treatment
Andrews, C.M., C.M. Grogan, B.T. Smith, A.J. Abraham, et al. 2018. Medicaid benefits for addiction treatment expanded after implementation of the Affordable Care Act. Health Affairs 37, no. 8: 1216–1222.
For this study, authors surveyed Medicaid programs in all states and the District of Columbia regarding their addiction treatment benefits and utilization controls in 2014 and 2017, after the ACA’s parity requirements took effect. They found that an increasing number of states covered benefits for residential treatment and medications used to treat opioid use disorder under their state plan. The number of states imposing annual service limits on outpatient addiction treatment decreased by over half, and fewer states required preauthorization for many other services. This trend was present among both alternative benefit plans as well as standard ones.
This study used a random-digit-dial survey of adults age 19–64 with incomes below 138 percent FPL in two expansion states (Arkansas and Kentucky) and one non-expansion state (Texas) conducted over 2013–2016. It found that Medicaid expansion was associated with a 23 percentage point reduction in the proportion of adults with depression who were uninsured. It was also associated with significant reductions in delaying care or medications due to cost.
Olfson, M., M. Wall C.L. Barry, C. Mauro, and R. Mojtabai. 2018. Impact of Medicaid expansion on coverage and treatment of low-income adults with substance use disorders. Health Affairs 37, no: 8: 1208–1215.
This study used data for 2008–2015 from the National Survey on Drug Use and Health to examine changes in coverage and substance use disorder (SUD) treatment among low-income adults following Medicaid expansion. It found that the percentage of expansion state residents with SUD who were uninsured decreased by 14 percentage points between 2014 and 2015, compared to a 6.6 percentage point decline among their counterparts in non-expansion states. However, there was no corresponding increase in SUD treatment in either expansion or non-expansion states.
GAO looked at 2014 Medicaid Statistical Information System data for four expansion states: Iowa, New York, Washington, and West Virginia. It found that between 20 and 34 percent of expansion enrollees received behavioral health treatment in 2014, including psychotherapy and prescription drugs. Among individuals in these states diagnosed with opioid abuse or dependence, between 62 and 81 percent used some outpatient treatment services, and between 11 and 41 percent used medication-assisted treatment.
Maclean, J. C. and B. Saloner. 2017. The effect of public insurance expansions on substance use disorder treatment: Evidence from the Affordable Care Act. April 2017. Bonn, Germany: IZA Institute of Labor Economics.
This study used administrative data from the Treatment Episodes Data Set for 2010–2015, and the Medicaid State Drug Utilization Data (SDUD) for 2011–2015. It found that following Medicaid expansion, there was no evidence of increased admission to specialty treatment for substance use disorder (SUD) in expansion states relative to non-expansion states. However, Medicaid-covered prescriptions for outpatient medications used for SUD treatment increased by 33 percent in expansion states relative to non-expansion states.
Wen, H., J. M. Hockenberry, T. F. Borders, B. G. Druss. 2017. Impact of Medicaid expansion on Medicaid-covered utilization of buprenorphine for opioid use disorder treatment. Medical Care 55, no. 4: 336–342.
This study examined 2011–2014 CMS Medicaid drug utilization files. It found that state adoption of Medicaid expansion was associated with a 70 percent increase in Medicaid-covered buprenorphine prescriptions and a 50 percent increase in Medicaid spending on these prescriptions, suggesting improved access to treatment. Increases in non-expansion states were not significant.
Saloner, B. S. N. Bandara, E. E. McGinty, and C. L. Barry. 2016. Justice-involved adults with substance use disorders: Coverage increased but rates of treatment did not in 2014. Health Affairs 35, no. 6: 1058–1066.
Using National Survey on Drug Use and Health data for 2004–2014, the authors found that the uninsured rate among adults who reported past-year criminal justice contact and met screening criteria for substance use disorder declined from 38 to 28 percent. However, overall treatment rates among this population were unchanged in 2014.
Access to other specific types of care and services
Harhay, M.N., R.M. McKenna, S.M. Boyle, et al. 2018. Association between Medicaid expansion under the Affordable Care Act and preemptive listings for kidney transplantation. Clinical Journal of the American Society of Nephrology, 13, no 7: 1069–1078.
Using 2011–2016 data from the United Network of Organ Sharing database, the authors looked at listings for kidney transplantation among adults with dialysis dependence. They found that expansion states had a 59 percent relative increase in Medicaid-covered preemptive listings following expansion. Non-expansion states had only an 8.8 percent relative increase. Additionally, the share of listings covered by Medicaid increased significantly (3 percentage points) in expansion states, and the increase was significant across race and ethnicity categories.
King, C.J., J. Moreno, S.V. Coleman, and J.F. Williams. 2018. Diabetes mortality rates among African Americans: A descriptive analysis pre and post Medicaid expansion. Preventive Medicine Reports 12: 20–24.
This study used data from the Compressed Mortality File of the Centers for Disease Control and Prevention to look at the difference in age-adjusted diabetes mortality rates among African Americans before and after Medicaid expansion. It found a slight reduction in diabetes mortality following Medicaid expansion: from 41.14 per 100,000 for 2008–2010 to 38.94 for 2014–2016. Across states, the change in mortality rates ranged from a decrease of 15.43 per 100,000 to an increase of 9.53 per 100,000. Rates declined in 16 of the 24 expansion states included in the study, and in 8 states that did not expand coverage.
Hospital administrative data for 2010–2015 showed that Medicaid expansion was associated with improved receipt of timely care among hospital patients with five common surgical conditions; specifically, a 1.8 percentage point increase in the probability of early uncomplicated presentation with common diagnosis and a 2.7 percentage point increase in the probability of receiving optimal care management.
The authors used data on prescription fills in the 50 states and the District of Columbia for 2008–2018 to examine the effects of Medicaid expansion on access to diabetes medications. They found that expansion was associated with 30 additional Medicaid-covered diabetes prescriptions filled per 1,000 compared to non-expansion states. Additionally, Medicaid-covered prescription fills for insulin and metformin each grew by 40 percent following expansion.
The authors examined data from the National Cancer Database for the periods 2004–2009 and 2011–2014, finding that women age 21 to 26 with gynecologic cancer were more likely to be insured and diagnosed at an early stage of disease following the ACA. However, privately insured women were more likely to be diagnosed at an early stage and receive fertility-sparing treatment than publically insured or uninsured women both before and after the ACA.
Ghosh, A., K. Simon, and B. D. Sommers. 2017. The effect of state Medicaid expansions on prescription drug use: Evidence from the Affordable Care Act. January 2017. Cambridge, MA: National Bureau of Economic Research.
Using 2013–2015 data from an all-payer pharmacy transaction database, this study found that in the first 15 months of Medicaid expansion, Medicaid-covered prescription drug utilization increased by 19 percent in expansion states relative to non-expansion states. The largest increases in Medicaid-covered prescriptions were for diabetes medications, contraceptives, and cardiovascular drugs. Increases were greatest in geographic areas with high pre-ACA uninsured rates and with large Hispanic and black populations. There were no significant reductions in prescriptions among uninsured, Medicare, or privately insured populations.
Effect of alternative approaches to expansion
This study used 2009–2016 American Community Survey (ACS) data to look at coverage effects of Indiana’s alternative approach to Medicaid expansion. It found little evidence to indicate that Indiana’s waiver program features (e.g., premiums, disenrollment and lock out for non-payment) caused smaller coverage effects as compared with traditional expansion states. Relative to pre-ACA uninsured rates, Indiana’s coverage gains following the Medicaid expansion were smaller than gains in neighboring expansion states, but larger than gains in non-neighboring expansion states (e.g., Arizona, Delaware, and North Dakota).
The authors collected survey data from low-income adults in three states in 2016: Kentucky, which expanded Medicaid; Arkansas, which expanded Medicaid through a Medicaid-funded exchange plan premium assistance; and Texas, which did not expand. They found that by the end of 2016, the uninsured rate in Kentucky and Arkansas declined by more than 20 percentage points relative to that in Texas. Among previously uninsured individuals, gaining coverage was associated with a 41 percentage point increase in the likelihood of having a usual source of care, a 23 percentage point increase in the likelihood of being in self-reported excellent health, and a $337 decrease in average annual out-of-pocket spending.
Sommers, B. D., R. J. Blendon, and J. Orav, 2016. Changes in utilization and health among low-income adults after Medicaid expansion or expanded private insurance. JAMA Internal Medicine 176, no. 10: 1501–1509.
Using survey data collected in Kentucky, Arkansas, and Texas from November 2013 through December 2015, this study looked at changes in utilization and health following Medicaid expansion. It found that in 2015, the second year of expansion, Kentucky and Arkansas both saw significant changes in coverage and access. Expansion was associated with a 22.7 percent decrease in the uninsured rate; significant increases in access to primary care, outpatient utilization, preventive care, improved health quality, and improved self-reported health; and, significant decreases in emergency department use. There were few differences between the traditional expansion state (Kentucky) and the state using an alternative approach to expansion (Arkansas).
The authors conducted a telephone survey between November and December 2013 to look at access to care and affordability paying for medical care among low-income adults. They found that in two expansion states, Kentucky and Arkansas, difficulty paying for medical care and skipping medication due to cost declined and the share of adults with chronic conditions who obtained regular care increased. There were few differences between the traditional expansion state (Kentucky) and the state using an alternative approach to expansion (Arkansas).
Effect of expansion on other measures of well-being
Using Michigan Medicaid administrative data as well as TransUnion consumer credit history information, this study examined the effect of the ACA on the financial well-being of newly eligible Medicaid beneficiaries. It found that enrollment was associated with reductions in unpaid bills, over limit credit card spending, delinquencies, and public records including evictions and bankruptcies. Individuals with greater medical need experienced the largest improvements.
Blavin, F., M. Karpman, G. M. Kenney, and B. D. Sommers. 2018. Medicaid versus marketplace coverage for near-poor adults: Effects on out-of-pocket spending and coverage. Health Affairs 37 no. 2: 299–307.
This study used Current Population Survey data for 2011–2016, and from the ACS for 2010–2015. It found that among adults with income between 100 and 138 percent FPL, living in an expansion state (relative to a non-expansion state) was associated with a $344 reduction in average out-of-pocket spending, a 4.1 percentage point decrease in the likelihood of having out-of-pocket spending in excess of 10 percent of income, and a 7.7 percentage point decline in the probability of having any out-of-pocket spending at all.
This study examined survey responses from 2013 to 2017 from low-income households who used free online tax preparation software when filing their taxes. It found that low-income families in financial stress who became eligible for Medicaid saved more of their tax refund. Low-income families that were not financially stressed did not make changes to their saving habits after becoming eligible for Medicaid.
The authors used national data on payday loans from 2009 through early 2014 obtained from the Community Financial Services Association of America. They found that following early Medicaid expansion in California, there were significant reductions in the number of loans and number of unique borrowers per month. There was also a significant reduction in the amount of payday loan debt in early expansion counties in California relative to non-expansion counties nationwide.
Brevoort, K., D. Grodzicki, and M.B. Hackman. 2017. Medicaid and financial health. November 2017. Cambridge, MA: National Bureau of Economic Research.
Using data collected from credit records, the authors found that Medicaid expansion reduced unpaid medical bills sent to collection by $3.4 billion in the first two years. Individuals’ improved financial health led to better terms for available credit valued at $520 million per year.
The authors used credit bureau data to look at the effects of Medicaid expansion on personal finance, finding that individuals in expansion states experienced improved credit scores and reduced past due balances; and were less likely to experience a medical collection of over $1,000, have one or medical bills go to collection, have derogatory balances at any time, or file for bankruptcy.
McMorrow, S., J. A. Gates, S. K. Long, and G. M. Kenney. 2017. Medicaid expansion increased coverage, improved affordability, and reduced psychological distress for low-income parents. Health Affairs 36, no. 5: 808–818.
This study used 2010–2015 National Health Interview Survey data to examine the effects of Medicaid expansion for low-income parents. It found that between 2010 and 2015, Medicaid expansion resulted in increased coverage and decreased psychological stress and problems paying medical bills. There were no significant effects on health status, affordability of prescription drugs, or mental health care, and only limited effects on increased use of care overall.
Spillover effects on other public programs
This study examined rates of employer-sponsored insurance following Medicaid expansion using June 2013 through March 2017 Health Reform Monitoring Survey data. It found that between June 2013 and March 2017, offer rates for employer-sponsored insurance remained stable and take-up rates increased. The share of workers with family incomes below 138 percent FPL who had employer-sponsored insurance remained the same, and uninsured rates declined.
Using data from the Medical Expenditure Panel Survey for 2008–2014, this study found no relationship between increases in insurance coverage at the local level and access to care for adults in the area that continuously had health insurance over the period. Specifically, there was no relationship across eight measures of access (e.g., receipt of preventive care) and no relationship in vulnerable subpopulations, including Medicaid beneficiaries and individuals residing in health care professional shortage areas.
McInerney, M., J. M. Mellor, L. M. Sabik. 2017. The effects of state Medicaid expansions for working-age adults on senior Medicare beneficiaries. American Economic Journal: Economic Policy 9, no. 3: 408–438.
This study examined the effect of Medicaid expansions on health care spending and utilization among Medicare beneficiaries using data from the Medicare Current Beneficiary Survey. It found that a 1 percentage point increase in the share of non-elderly adults eligible for Medicaid was associated with a $477 reduction in average beneficiary spending for individuals dually eligible for Medicare and Medicaid.
This study used data from the American Community Survey as well administrative data from the Women, Infants, and Children (WIC) and Supplemental Nutrition Assistance Program (SNAP) to look at the effects of Medicaid expansion on enrollment in other programs. It found that while enrollment in means-tested programs decreased after 2014 regardless of whether a state expanded Medicaid, states that both expanded Medicaid and conducted Medicaid enrollment outreach experienced smaller SNAP and WIC enrollment decreases than other states.
Sen, A.P., and T. DeLeire. 2018. How does expansion of public health insurance affect risk pools and premiums in the market for private health insurance? Evidence from Medicaid and the Affordable Care Act marketplaces. Health Economics: 2018: 1–26.
This study used several different data sources, including public use data available from the Center for Consumer Information and Insurance Oversight at the Center for Medicare & Medicaid Services to look at the effect of Medicaid expansion on premiums for plans on the exchange. It found that exchange plan premiums are 11 percent lower in Medicaid expansion states, after controlling for demographic and health characteristics and measures of health access.
The authors used data for 2010–2015 from the Social Security Administration and the American Community Survey to look at trends in Supplemental Security Income (SSI) participation following expansion. They found that in states that expanded Medicaid (allowing non-elderly adults to qualify without having to obtain a disability determination through the SSI program), SSI participation decreased by 3 percent relative to non-expansion states after 2014.
This study used a combination of crime-related data sets for 2010–2015 to look at the relationship between access to health care and criminal behavior following Medicaid expansion. It found that following Medicaid expansion, reported instances of violent and property crime per 100,000 people fell by 5 percent in expansion states and 3 percent in non-expansion states, a statistically significant difference. Crime reductions were even more pronounced in counties that experienced the largest decreases in uninsured rates following expansion.