This paper reviews surveys that provide estimates of the uninsured population in the United States. Currently, seven surveys can be used to make nationally representative estimates of the number of people without health insurance coverage. Some of the surveys collect health insurance information in the context of obtaining general information on health care, while other surveys are focused on other topics such as labor force participation and public assistance program participation. This paper includes a discussion of why the estimates from the various surveys differ. The most widely used survey that collects information on health insurance coverage is the Current Population Survey (CPS), conducted by the Census Bureau. The most recent estimates from the CPS suggest that 44.3 million Americans were uninsured in 1998. Besides the CPS, a number of other surveys collect information on the uninsured population. They include the Survey of Income and Program Participation (SIPP), Behavioral Risk Factor Surveillance System (BRFSS), Community Tracking Study (CTS), Medical Expenditure Panel Survey (MEPS), National Health Interview Survey (NHIS), and the National Survey of America's Families (NSAF). Estimates of the uninsured from these surveys range from 19 million to 44 million and vary depending on the time frame the survey covers. It is important to understand the differences in the estimates of the uninsured population from the various surveys. The projected cost of implementing policy proposals depends on the estimates of the number of people affected by the proposals; for instance, the allocation of funding for the State Children's Health Insurance Program (S-CHIP) depends heavily on the available estimates. In addition, the estimated effectiveness of policy proposals to reduce the uninsured population will be accurate only if the correct count is known and the precise make-up of the uninsured population is understood. A number of states have started to question the validity of the uninsured estimates from the CPS, and other surveys, because of the small sample size in many states. As a result, some states have begun to conduct their own surveys to determine the number of uninsured residents. States that regularly conduct their own surveys include Florida, Massachusetts, Minnesota, New Mexico, Oregon, Vermont, and Wisconsin. Unfortunately, the various state surveys are not easily comparable. Research needs to continue to increase understanding of the differences among the surveys and to improve on methodologies to count the uninsured, as the future of public programs, such as S-CHIP and other state and local initiatives to expand health insurance coverage, depends on the accuracy of these estimates. Whatever survey is used, the results show that a substantial number of Americans do not have any health insurance coverage, and the number has been growing
