1. Because of these revisions and a change in the sample framework for the survey in 1995, it is difficult to compare estimates done before and after that year. Researchers believe that these revisions, coupled with the change in the sample framework for the survey in 1995, may have increased the number of persons reporting that they were insured (Swartz 1997). As a result, estimates before the 1995 CPS are not fully comparable to more recent estimates. However, at least one researcher has made adjustments to the CPS data in order to make more valid comparisons of health insurance coverage before and after the 1995 revisions (Fronstin, 1997b).
2. Including the elderly increases this estimate by only 300,000 individuals, since nearly all elderly are covered by Medicare. If the elderly are included, then 15.4 percent of the total population was without health insurance in 1995.
3. As cited in Monheit (1994).
4. Of course, the MEPS could have similar reporting problems to the CPS. However, the MEPS health insurance questions are much more detailed than the CPS questions, and interviewers are trained specifically on asking health related questions. The MEPS study is discussed in more detail later in this chapter.
5. Personal correspondence with Linda Bilheimer of CBO and Kathy Swartz of the Harvard School of Public Health, September 15, 1997.
6. One reason suggested by researchers for why people may not realize they are covered by Medicaid is that they are enrolled in a managed care program and, therefore, report that they are covered by the managed care company. If, indeed, this is occurring, then the problem of Medicaid underreporting could get worse as more states adopt Medicaid managed care programs.
7. For example, if most persons are enrolled for only 10 of 12 months, then the number of persons ever enrolled in the year should be adjusted downward by almost 17 percent to be comparable to a point-in-time estimate. With additional HCFA(now known as CMS) data, it is possible to calculate the average monthly number of persons enrolled in Medicaid.
8. HCFA(now known as CMS) also reports the number of Medicaid "recipients." Recipients, though, are defined by HCFA(now known as CMS) as the subset of enrollees, or eligibles, that utilized services during the year
9. Some researchers (for example, see Thorpe 1997a and 1997b) cite the number of children enrolled in Medicaid in 1995 according to the CPS as 13.8 million rather than 16.5 million. These researchers are reporting the number of children covered only by Medicaid during the previous year, thus excluding children that were covered by both Medicaid and private insurance during that period.
10. Nationally, enrollees exceeded recipients by 14 percent (HCFA(now known as CMS) 2082 tables for 1995).
11. They further add that analyses of people in poverty, people receiving welfare (AFDC), and people experiencing unemployment have been consistent in finding that most people who experience any of these situations, do so for short periods of time (see, for example, Bane and Ellwood 1986; O'Neill, Bassi, and Wolf 1987; Akerlof and Main 1980).
12. The 1992 panel was extended about one year, to 40 months.
13. One exception to this rule is that persons who die are given weights. Also, an important implication of this weighting design is that almost all infants born during a calendar year will have a zero-weight for that calendar because they are not part of the population on January 1. As a result, infants will be underrepresented in the SIPP data, which is of particular concern because infants have been a key target group for Medicaid expansions over the last decade.
14. Sometimes only a count or a percent is presented in the tables, but not both, because that is all a researcher reported. We do not attempt to calculate implied percents or counts because the denominator over which they are calculated is not always reported and not always obvious.
15. Bennefield did not cite the denominator for his calculation of the SIPP estimate of all persons who were uninsured. Based on other SIPP literature, the universe of all persons represents about 250 million persons. This would suggest that there were about 37 to 38 million uninsured at a point in time, an often cited figure.
16. Interview of Chuck Nelson and Bob Bennefield of the Census Bureau, conducted by Dave Baugh and Roger Buchanan of HCFA(now known as CMS) (July 23, 1997).
17. The comparable estimates for all persons were 7.7 percent (Bennefield, 1996c) and 4 percent (Bennefield 1995), respectively.
18. The comparable estimates for all persons were 21.2 percent (Bennefield, 1996b) and 26.5 percent (Bennefield 1995), respectively. That the differences between the 1-year and the 32-month estimates for adults was less than that for children suggests that there was less churning of the uninsured for adults.
19. Point-estimates of the uninsured using the SIPP fell somewhere between the uninsured throughout and the uninsured in at least one month estimates. In 1993, 13.5 percent of children were uninsured at any given time (Bilheimer 1997).
20. Swartz (1994) provides a useful overview of the dynamic of people without health insurance, along with references to earlier works on this topic.
21. A similar analysis of the MEPS with the same findings can be found in Vistnes and Monheit (1997).
22. Full-year 1996 MEPS estimates of the uninsured were not available as of the writing of this paper, but are planned once all interviews pertaining to 1996 are completed.
23. One of the definitional differences they cite is that the CPS assumes all AFDC recipients and most SSI recipients are enrolled in Medicaid, whereas MEPS usually does not. In addition, CPS counts children of adults covered by Medicaid as insured, whereas for these preliminary estimates, MEPS does not (unless their families reported them as covered). Finally, unlike MEPS, CPS counts as uninsured military veterans whose source of coverage is the Department of Veterans Affairs.
24. Missing Medicaid coverage for this group -- that is, those covered by private insurance and Medicaid -- would not affect the estimates of the uninsured because this group is reported as receiving private insurance.
25. The two samples are not independent, in that they tend to be pulled from the same neighborhoods; therefore, the doubled sample size yields something less than a proportionate reduction in variance.
26. The West South Central region includes the following states: Arkansas, Louisiana, Oklahoma, and Texas.
27. The East North Central region includes Illinois, Indiana, Michigan, Ohio, and Wisconsin.
28. The imputation equations predict which children will be uninsured in one or more months over the 2-year period on the basis of their demographic and economic characteristics. Researchers generally do not use the SIPP alone for state-level estimates because not all states in the SIPP are uniquely identified and because SIPP's relatively small sample sizes make resulting estimates imprecise. Even the CPS, with its larger sample sizes, does not support precise estimates in most of the smaller states.