The Effect of Medicaid Expansion on Marketplace Premiums

This issue brief examines whether and how much of the Marketplace premium differences between expansion and non-expansion states are  due  to the direct impact of states’ decisions to expand Medicaid. We estimate that Marketplace premiums are about 7 percent lower in expansion states, controlling for differences across states in demographic characteristics, pre-ACA uninsured rates, health care costs, and state policy decisions other than Medicaid expansion (e.g., allowing transitional policies, rating area design), and limiting the analysis to neighboring counties, which might be expected to have similar populations.