A number of important policy questions depend on obtaining valid national, state, and local estimates of the insurance distribution of adults and children. Sound estimates of the number of uninsured and their characteristics are critical to developing valid projections of the costs and coverage impacts associated with implementation of the Affordable Care Act (ACA) and related health reforms. In addition, estimates of the extent to which Medicaid and the Children‘s Health Insurance Program (CHIP) are reaching their target populations provide useful information to guide policy actions at both the state and federal levels of government. Having valid coverage estimates at the state level is also critical to obtaining sound projections of federal outlays given variation in federal matching rates across states. Moreover, understanding variation in coverage rates and the distribution of the uninsured across local areas provides federal, state, and local policymakers with vital information for projecting the increased demand for health care resulting from the ACA and for the need for safety net providers.