For 2007 and prior, we modeled health insurance coverage as measured by the Annual Social and Economic Supplement (ASEC) of the Current Population Survey (CPS). Starting with 2008 SAHIE, we use American Community Survey health insurance estimates.
The CPS ASEC is the official source for national estimates of health insurance coverage. The CPS ASEC provides annual national and state-level estimates based on a sample of about 100,000 addresses. It asks about health insurance coverage in the previous calendar year. People are considered insured if they were covered by any type of health insurance coverage for part or all of the previous year, and they are considered uninsured if they were not covered by any type of health insurance for the entire year. People with no coverage other than access to Indian Health Service are also considered uninsured.
For more information about health insurance coverage see the health insurance main page.
Compared with other national surveys, the CPS ASEC estimate of the number of uninsured more closely approximates the number of uninsured at a specific point in time during the year than the number of uninsured for the entire year. For more details see "People with Health Insurance: A Comparison of Estimates from Two Surveys" [PDF – 68k] (Survey of Income and Program Participation Working Paper 243, June 2004).
The CPS ASEC universe includes the civilian noninstitutional population of the United States and members of the armed forces in the United States living off post or with their families on post. It excludes all other members of the armed forces and treats college students living in dormitories as residing in their parental homes. It does not include observations for most counties. Of the more than 3,100 counties in the United States, about 1,200 counties are in the sample. In the design, some counties represent a group of counties, while others represent only themselves. To use the data at the county-level we adjust the sample "weights" (the number of people represented by each sample person) so that each county is self representing.
We model a three year average of the CPS ASEC centered on the year of interest. For example, for the 2007 model we averaged estimates for 2006, 2007 and 2008 obtained from the 2007, 2008 and 2009 CPS ASECs. We used estimates reflecting the results of follow-up verification questions and implementation of Census 2000-based population controls. Beginning with the 2001 CPS ASEC, the estimates also reflect the implementation of a sample expansion that increased the number of responding households by 28,000 to about 78,000 households.
For more information about characteristics of the CPS and the ASEC see the CPS main page.