According to a recent report:

• 10% of uninsured people (3.1 million) fall into a “coverage gap” of earning too much to qualify for Medicaid but not enough to qualify for premium tax credits under the Affordable Care Act (ACA), because they live in one of the 20 states that chose not to implement Medicaid expansion
• In states that expanded Medicaid, 40% of the nonelderly uninsured population is eligible for Medicaid, versus just 13% in states that have not expanded Medicaid
• No one falls into a coverage gap in the states that expanded Medicaid
• In states that did not expand Medicaid, 19% of uninsured people fall into the coverage gap

Source: "New Estimates of Eligibility for ACA Coverage among the Uninsured," The Henry J. Kaiser Family Foundation, October 13, 2105, http://kff.org/uninsured/issue-brief/new-estimates-of-eligibility-for-aca-coverage-among-the-uninsured/?utm_campaign=KFF:%202015%20October%20ACA%20Uninsured%20Eligibility&utm_source=hs_email&utm_medium=email&utm_content=22790255&_hsenc=p2ANqtz-9oPzaSj1CFCOGc01MKFpk1I2M_DDr_zf1gTddY494ETI_4iKiIwukUbOy3suQtQMjEaH7rfRhCcSHih-0eVXrxTA8cvg&_hsmi=22790255