If respondents answer the CPS health insurance questions as intended -- that is, as coverage at any time during the previous year -- then estimates of the uninsured should be interpreted as those without coverage throughout the previous year. However, some researchers believe that the CPS estimates of the uninsured are too high and, thus, that respondents may be reporting their health insurance status as of the interview date. Swartz (1986) compared CPS estimates of the uninsured with estimates from three other surveys that asked respondents about their health insurance coverage as of the interview date. The three other surveys were: the National Medical Care Expenditure Survey (1977), the Health Interview Survey (1978), and the National Medical Care Utilization and Expenditure Survey (1980). She found that the CPS estimates more closely resembled the point-in-time estimates of these surveys. CBO agreed with Swartz and considers its own CPS-based estimates of the uninsured to be closer to a point-in-time estimate rather than an estimate of those uninsured throughout the previous year (Bilheimer 1997).
Although the CPS estimates may resemble point-in-time estimates of the uninsured, there is evidence that some respondents interpret the questions correctly and report their status as of the previous year. For example, in 1995, 15 percent of children enrolled in Medicaid according to the CPS also reported coverage by private health insurance (Fronstin 1996). These children are probably not reporting their current status, since it is unlikely that this many children would be covered by Medicaid and private insurance at the same time. Instead, they are probably reporting their status as of the previous year when they were covered by private insurance for part of the year and Medicaid for part of the year. Other researchers provide additional evidence that many respondents interpret the questions correctly. For example, Kronick (1989)(3) found that private employer-sponsored health insurance coverage in the CPS is more consistent with employment status in the previous year than in the interview month. In addition, the first round of the Medical Expenditure Panel Survey (MEPS), which asked respondents whether they were uninsured continuously from January 1, 1996 to their interview date 3 to 6 months later (and links their responses to employment related data), provided estimates that were strikingly similar to the CPS (Beauregard et al. 1977).(4)
In a more recent analysis, Bennefield (1996c) compared longitudinal data from the SIPP with the standard health insurance data from the CPS and with data from experimental questions on the March 1995 CPS that asked about current health insurance status. Bennefield's results indicated that CPS respondents interpreted the standard health insurance questions correctly and provided their health insurance status as of the previous year. However, he found that respondents may have had recall problems and failed to report some coverage and, as a result, the CPS estimates of the uninsured looked more like point-in-time estimates. Some researchers, though, doubt the usefulness of the experimental health insurance questions on the CPS because they yielded extremely large numbers of uninsured.(5)
Long and Marquis (1996) compared the 1993 March CPS estimates of the uninsured in 10 states with the findings from the Robert Wood Johnson Foundation (RWJF) Family Health Insurance Survey. The RWJF survey was administered to approximately 2,000 families each in Colorado, Florida, Minnesota, New Mexico, New York, North Dakota, Oklahoma, Oregon, Vermont, and Washington during 1993. The uninsured and those covered by Medicaid were oversampled. The content includes considerable detail on insurance status -- both current and throughout the previous year. Across the 10 states included in the RWJF survey, the CPS estimate of the uninsured for all persons (14.7 percent) fell between the RWJF estimate of the currently uninsured (15.7 percent) and the uninsured throughout the previous year (12.2 percent). Long and Marquis also examined each state individually and found that for 9 of 10 states, the CPS measure fell between the RWJF current and throughout the previous year measures; in the remaining state, the CPS estimate was above the RWJF estimate of the currently uninsured by only 0.2 percentage points. Long and Marquis concluded that using the CPS as if it were a measure of the currently uninsured generally will understate estimates of the uninsured at a point in time. However, the CPS measure was considerably closer to the RWJF currently uninsured estimate than the uninsured throughout the previous year. The CPS estimate was only 6 percent below the RWJF currently uninsured estimate, but 20 percent above the RWJF estimate of the uninsured throughout the previous year.
Overall, though, most researchers tend to agree that the CPS probably contains a mixed bag of reporting -- that is, some respondents report health insurance status during the previous year, some report it as of the interview date, and some fail to report it altogether -- which, in the end, yields estimates that are probably best interpreted as health insurance status at a point in time.