Data from Medicaid eligibility, enrollment, and claims and the new state CHIP can be linked to provide longitudinal tracking of a child or family’s health care services or lack of services. For example, a state could track the Medicaid or CHIP enrollment of a child whose mother left AFDC. Since it is unlikely that many families leaving TANF will promptly go to jobs with sufficient health benefits or wages above the Medicaid and CHIP guidelines, that is, 200 percent of the federal poverty level in most states but 350 percent of the federal poverty level in some Medicaid expansion programs, lack of Medicaid coverage of a child in an AFDC/TANF leaver family may indicate that the child is at risk of having no health care coverage. If Early and Periodic Screening and Diagnostic Testing (EPSDT) services also are recorded in the Medicaid files, similar linkages with welfare data will allow tracking of the utilization of preventive services for these low-income children. Linked administrative data from AFDC/TANF and Medicaid have also been used as the sample frame for complementary survey research, which can gather indicators of health status or measures of health care utilization and provide more in-depth measures. For example, the Next Generation, a project conducted by Manpower Demonstration Research Corporation (2000), will use survey data from 10 studies to obtain a more comprehensive perspective about the effects of welfare reform on health outcomes. Variables about health will be measured through survey questions, but the project also will include the existing administrative data used in each of the 10 studies.
Using administrative data from Medicaid and CHIP (or other health-related supplemental services such as the Food Stamps Program or WIC) requires attention to a variety of considerations.
One must consider the populations in the data sets in relation to the population of interest for the study. Specifically:
Determining what cases are to be included in the population of study. Study populations that can be drawn from Medicaid or CHIP files include: applicants, eligible cases, open cases, closed cases, cases closed with high risk, timelimited or sanctioned cases, or reentry cases.
Within the group of eligible children are several subgroups that might be of interest. One group for Medicaid is those children actually enrolled. This subgroup of enrolled children includes a second subgroup of children receiving services. This group is not representative of all children enrolled, or all children eligible, or all low-income children in need of health care.
Medicaid data can be used to extend the analysis of the impact of welfare reform beyond the TANF population because the Medicaid eligibility pool is larger than the TANF eligibility pool. For example, California uses data files on Medicaid recipients as the core of its data sharing/data integration initiatives (National Conference of State Legislators, 1999). This strategy can allow evalu-