Estimating the Number of Individuals in the U.S. Without Health Insurance. Survey Revisions Through Time

01/31/2005

As noted earlier, there have been changes to the CPS over time that have clarified the estimates of specific insurance classes as well as changes that have affected the measurement of overall levels of insurance coverage. These changes have included the following:

  • In the late 1980s, estimates of private insurance were refined with respect to what was employer-sponsored, by broadening the universe of who were asked this question beyond just workers and their family members. In addition, questions were also added at the household level to pick up coverage of children that might have been missed (employersponsored insurance) from outside the household and Medicaid).
  • Several major revisions to the CPS occurred in the mid 1990s. Census converted to a CATI/CAPI process, which has been thought to increase detection of insurance coverage. In addition, beginning with the March 1995 CPS, the questionnaire was changed to expand the categories of coverage a person could have. This allowed for a more accurate detection of Medicaid (although it resulted in fewer Medicaid covered persons as the “other government coverage” categories increased), as well as more accurate nonhierarchical counts of persons covered by private insurance (both employer sponsored and individual).6
  • In March 2000, the survey added a verification question to clarify the number of uninsured.
  • In March 2001 the survey also added a question to pick up coverage under the State Children’s Health Insurance Program (SCHIP).
  • March 2002 saw the additional change of weights based on the 2000 Census.
  • While the March 2003 CPS saw some changes to such fields as industry, occupation, and racial classification, the insurance portion of the survey remained the same as in March 2002 and March 2001. March 2004 followed the format and classifications found in March 2003.

Although the improvements to the CPS over time have been extremely helpful, they have made it more difficult to model trends over time. In addition, there are specific issues with certain insurance coverage estimates from the CPS - in particular, the reported Medicaid population is much lower than that implied by program statistics from the Centers for Medicare and Medicaid Services (CMS), and lower than that found in other surveys such as MEPS and the SIPP.

Using the most recent surveys (March 1995 through March 2004), we have attempted to adjust for the survey changes, including insurance verification and SCHIP coverage, as well as for the shortfall in Medicaid enrollees captured by the survey. In addition, we have imposed consistent definitions on certain types of insurance (such as a consistent minimum age to be a policy holder with employer-sponsored insurance). For those adjustments that represented a change in the survey, we have used the more current data in order to adjust the data from earlier survey years.

The adjustments were made to a uniform set of file extracts for the period March 1995 through March 2004. The initial files contained no adjustments; merely using the insurance definitions and weights provided by Census for each year but recoded into a more standard format. The following adjustments were then made to the files: a) updating the survey weights to reflect the new decennial Census, b) adjustments for employer sponsored insurance (age of policy holder, coverage from outside of household), c) adjustment for verification and SCHIP, and d) adjustment for Medicaid undercount. These adjustments are briefly described below, and are addressed in more detail in the appendix of this document (See “Technical Appendix: A Longitudinal Model of Health Insurance: An Update of Employer Sponsored Insurance, Medicaid, and the Uninsured”).


For example, the survey update allowed identification of spouses who had insurance in their own name from their own employer in addition to being listed as a dependent on another policy, a change that increased the counts of persons with employer-sponsored insurance policies.

View full report

Preview
Download

"report.pdf" (pdf, 121.72Kb)

Note: Documents in PDF format require the Adobe Acrobat Reader®. If you experience problems with PDF documents, please download the latest version of the Reader®

View full report

Preview
Download

"TechAppendix.pdf" (pdf, 366.49Kb)

Note: Documents in PDF format require the Adobe Acrobat Reader®. If you experience problems with PDF documents, please download the latest version of the Reader®