Welfare Reform/Child Well-Being Administrative Data Linking. Study Population


Because the intent of this study was to examine Medicaid Utilization before and after employment, selection of the study population was critical. The initial population of SCDSS AFDC/TANF clients was selected based upon a number of criteria.

  1. First, all cases must have been coded as an AFDC/TANF case, though not every client associated with a particular case had to be coded as an AFDC/TANF participant.
  2. Second, the case had to be closed for earned income (closure code of 'EI') within a time frame that allowed for adequate tracking using quarterly ESC Wage Match data. Given the availability of ESC data at the time of the study, these cases closed in June 1996, September 1996, or December 1996. No restriction on subsequent returns and closures was imposed.
  3. In order to provide adequate time frames to detect differences in utilization and to control for seasonality, the study population required l-year of pre-employment activity (and 1-year of post employment activity - see next step). Therefore third, each of these cases must have been an active AFDC/TANF case for at least one year prior to the closure date.
  4. The resulting population from step 3 was then matched to the quarterly ESC Wage Match information. In order to be retained, the case must have had at lease one adult earning wages in the first and last quarters of the post closure year. Continuous employment however was not a requirement.
  5. After controlling for one-year pre-employment and one-year post employment and the other above criteria, the resulting population was 1,635 clients. These clients then underwent cleaning to insure that any possible changes in name, etc. were captured for linking purposes. Date constants were also added to mark the beginning of the "pre-" period, the closure date, and the ending of the "post-" period.
  6. The 1,635 starting population was next linked to the Medicaid Eligibility files. The matching criteria used varying combinations of a number of key identifiers: SSN, full name, and date of birth. Numerous quality control checks were performed to ensure that clients were matched correctly. 1,557 of the 1,635 SCDSS clients identified linked to the Medicaid Eligibility files resulting in a 95.2% match rate.
  7. Because varying Medicaid Eligibility coverage can affect results, the Medicaid Eligibility coverage was next examined for any biases. This study used a working definition of Medicaid Eligibility coverage of 700 or more days of Medicaid eligibility (2 years less 1 month). One thousand and thirty one clients (1,031) met that definition.
  8. One result of using Medicaid coverage definition of 700+ days is that it eliminated most of the newborns. While there, is a great deal of interest, of course, about newborns, it was felt that within the confines of this study that an adequate comparison could not be done and that it would bias the study. All pregnancy related and post-partum claims were also excluded. Again, the purpose was to eliminate any bias introduced by a roughly nine (9) month gestation period within the context of a two-year study. For example, impact of conception in the post-period would fall outside the study's time frame, while pregnancies from the pre-period might result in deliveries in the post period. Differences in the lengths of individual pregnancies confounded our inability to determine dates of conceptions necessary to account for these claims. Therefore all claims of these types were excluded to eliminate their confounding effects. In addition, mothers who are pregnant and newborns require higher numbers of doctor's visits and other types of claims.. Over a two year time period that could again bias the results by inflating the number of claims. Because of the natural "aging" process and the 2-year time period, pregnancy related and post partum claims may not be "evenly distributed" across the period. For example, mothers who had a baby in the first year (pre-employment) period were less likely to have a baby in the next period (or post-employment) period.
  9. Those clients who met the 700 or more day requirement were next linked to the Medicaid Services files. Claims essentially were divided into three types: HIC (physician, clinic, and laboratory claims), Outpatient (which includes both emergency and non-emergency room visits) and Inpatient hospitalization. For HIC claims, only-physician visits were included. Outpatient claims were further sub-categorized as emergency and non-emergency visits. In addition, outpatient and HIC claims were summed thereby providing an index for ambulatory care utilization.
  10. For each claim type and combination of claims, the number of paid claims for the pre-employment and post-employment periods were summed.