Under the Affordable Care Act (ACA), states can expand Medicaid eligibility for nonelderly people up to 138 percent of the federal poverty level (FPL). As of March 2018, 31 states and the District of Columbia had expanded and 19 states had not. If the remaining 19 states were to fully implement a Medicaid expansion in 2019 and all else stayed the same, we estimate that between 4.3 and 4.7 million fewer people would be uninsured, Federal spending on health care would increase by between $32.1 billion and $37.8 billion, while state spending on Medicaid would increase by between $2.3 billion and $3.0 billion. This additional state spending would fully or largely be offset by savings in other areas.