Between 2012 and today the US has been conducting a natural experiment on herself. The US Supreme Court ruling on the Affordable Care Act allowed states to decide whether or not to expand Medicaid to 133% of federal poverty. Some stated did it and some didn't.... so we have a kind of case control study. Now that it's been several years, let's look at the data and see who made the better decision.
The Kaiser Family Foundation recently conducted a comprehensive review of the scientific literature and found that states that expanded Medicaid under the ACA had did better than their peers that didn't expand. In a nutshell, the report found that the states that expanded Medicaid improved healthcare insurance coverage, access to care, utilization, and health care affordability. Interestingly (for me at least) was the fact that states that expanded had better economic outcomes than those that didn't... including positive effects on state budgets, employment and the labor market.
Additionally, a New Health Affairs article found that there were no significant increases in spending from state funds as a result of expanding Medicaid (in the states that expanded). The Health Affairs study found that "... expansion states did not experience any significant increase in state-funded expenditures, and there is no evidence that expansion crowded out funding for other state priorities."
Statistically, states that expanded Medicaid had budget savings, revenue gains, and higher overall economic growth when compared to their peers that didn't expand Medicaid. Studies also found that expansion states had lower Medicaid spending per enrollee for the new ACA adult eligibility group compared to per-enrollee spending across all groups.
Medicaid expansion resulted in health insurance coverage gains among the low-income folks including specific vulnerable populations. Most research found that Medicaid expansion improved access to care, utilization of services, the affordability of care, and financial security among the low-income population (just as you'd expect).
The report is really well referenced. It's a great resource for folks looking for a one stop shop for data on the impact that Medicaid expansion has had over the last few years.
Above all, it's great information for policy makers as it provides objective evidence regarding the impact that Medicaid expansion had in states that expanded v those that chose not to expand.
Take a look and bookmark these two studies.