A Shared Destiny is the fourth in a series of six reports on the problems of uninsurance in the United States. This report examines how the quality, quantity, and scope of community health services can be adversely affected by having a large or growing uninsured population. It explores the overlapping financial and organizational basis of health services delivery to uninsured and insured populations, the effects of community uninsurance on access to health care locally, and the potential spillover effects on a community’s economy and the health of its citizens. The committee believes - it is both mistaken and dangerous to assume that the persistence of a sizable uninsured population in the United States harms only those who are uninsured.