In January 2014, the Affordable Care Act (ACA) will begin to offer new health insurance coverage options to millions of Americans, many of whom are currently uninsured. There is still considerable uncertainty, however, about how the coverage expansion will play out. Several states continue to debate whether to expand eligibility for their Medicaid programs as the ACA intended. To better understand the likely coverage effects of the ACA on Michigan’s insurance market, it is important to recognize the demographic characteristics of Michigan residents who will be most affected. This issue brief is intended to both describe the characteristics of these populations and project how the ACA will affect the overall picture of coverage in Michigan. Since there is still uncertainty about whether or not Michigan will move forward on an expansion of Medicaid, alternative projection scenarios are included.