September 10, 2009
12:01 a.m. Eastern Time
Respondents To The Current Population Survey Often Can't Accurately Recall Their Insurance Status Throughout The Previous Year
Widely Cited Census Bureau Estimates May Substantially Undercount Medicaid Recipients And Overcount Uninsured
Bethesda, MD -- Widely cited estimates from the U.S. Census Bureau likely overstate the number of uninsured people and understate the number of people with Medicaid coverage because of an inability of people to recall their insurance status accurately from the previous year, according to a study published today on the Health Affairs Web site. http://content.healthaffairs.org/cgi/content/abstract/hlthaff.28.6.w991
The Census estimates are derived from the Census Bureau's Current Population Survey (CPS). The Census Bureau is scheduled to announce the results of the 2009 CPS on September 10 at 10:00 AM ET.
The CPS, administered in February, March, and April each year, asks respondents whether they had health insurance coverage (including Medicaid) at any point in the previous calendar year. However, the CPS's long recall period (fourteen to sixteen months) can lead to inaccurate responses, report lead author Jacob Klerman, a principal associate at Abt Associates in Cambridge, Massachusetts, and coauthors.
According to Klerman and his colleagues, CPS responses are most inaccurate for those whose periods of Medicaid coverage in the previous year were relatively short and relatively early in the year, because those are hardest to recall. The researchers say that similar recall problems may affect CPS estimates of those covered by other types of health insurance in addition to Medicaid, and they call for research into whether other surveys, such as Census's American Community Survey, could provide better estimates of the uninsured.
Rejecting Two Traditional Interpretations Of The CPS
Klerman and coauthors reject the two competing interpretations of the CPS estimates that have dominated the literature to date. The first standard interpretation holds that people answer the CPS questions as they are instructed, so that the survey results indeed yield the number of people who did not have Medicaid or other health insurance for even one day in the previous calendar year. However, the CPS estimates are much higher than other surveys' all-year uninsurance estimates, and indeed are closer to point-in-time estimates of uninsurance produced by other surveys. For this reason, a second, point-in-time interpretation of the CPS data has developed, which holds that answers to the CPS reflect the insurance status of respondents on the date the questions are asked.
The researchers put forward evidence that both of these interpretations of the CPS data are inadequate. For example, among those who had Medicaid coverage at the time of the survey but who lacked Medicaid for all of the previous year, only a quarter reported having Medicaid coverage, a result inconsistent with the "point in time" interpretation. On the other hand, among those who lacked Medicaid at the time of the survey but who were covered by Medicaid at some point during the previous year, only a third reported Medicaid coverage -- a result inconsistent with the "previous-calendar year" interpretation.
After the embargo lifts, you can read the article by Klerman and coauthors at http://content.healthaffairs.org/cgi/content/abstract/hlthaff.28.6.w991
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