SEDS is a web-based system maintained by CMS since 2000 that collects new and total Medicaid and CHIP enrollment data from states on a quarterly basis. States must submit quarterly enrollment data within 30 days after the end of the fiscal quarter and aggregate annual data within 30 days after the end of the fourth quarter.46 This analysis uses quarterly and annual total enrollment data from three of the SEDS reporting forms and, to our knowledge, is the first analysis to do so.47
This report focuses on the 2007 to 2011 quarterly SEDS data on total enrollment (the unduplicated number of children ever enrolled during the quarter). Throughout the analysis, we define Medicaid enrollment to include both traditional Medicaid and Title XXI CHIP-funded Medicaid expansions. We define total Medicaid/CHIP enrollment to include enrollment in traditional Medicaid, CHIP-funded Medicaid expansions, and separate CHIP programs. Quarterly data before 2007 are excluded due to reporting errors and high item nonresponse rates.
Some quality issues are evident in the total enrollment data, including missing observations and likely reporting errors. We addressed quality issues in the quarterly data by imputing missing values and repairing reporting errors on a case-by-case basis. Our imputation strategy, which uses interpolation in most instances, is consistent with procedures that Mathematica developed while working with the annual SEDS data (Ellwood et al. 2003).48 Data points were also cross-validated using the Medicaid Statistical Information System and monthly Medicaid/CHIP enrollment data reports from the Kaiser Commission on Medicaid and the Uninsured (Kaiser 2011a; Kaiser 2011b). We made imputations on fewer than 5 percent of state-quarter observations and the final analysis file, with the imputations, was approved by CMS/SEDS analysts on March 30, 2012.
Two non-ELE states, Maine and Montana, are excluded from this analysis due to concerns about data reliability. Maine implemented a new Medicaid Management Information System in 2011 and identified problems in its enrollment data caused by reporting errors. It is currently working on this problem, but is not expected to submit revised data any time soon.49 Similarly, we found substantial variation in the Montana data from 2007 to 2011, although patterns in the 2009 to 2011 data could be partially explained by Medicaid/CHIP expansions and changes in economic conditions, according to the CMS Regional Office.50 We also conducted several statistical tests (for example, difference in fit, a diagnostic meant to show how influential a point is in a statistical regression) and determined that Montana was an outlier state, which indicated that it might not serve as an accurate counterfactual to ELE states. Although Montana had some influence on the regression model in the multivariate analysis, we found that our main results did not substantially change by its inclusion or exclusion. However, given the outlier tests and uncertainty over the validity of the state’s data, we excluded Montana from the descriptive and multivariate analyses.
Appendix C, Table C.1 contains the Medicaid and CHIP quarterly enrollment data for all ELE states from 2007 to 2011. Imputed enrollment values are noted.
46 Federal fiscal year quarters are as follows: first quarter, October 1 through December 31; second quarter, January 1 through March 31; third quarter, April 1 through June 30; and fourth quarter, July 1 to September 30.
47 All data files were downloaded in January 2012. There were also smaller state-specific downloads through March 2012, because some states revised their enrollment data.
48 For instance, if data from a particular quarter were missing or inconsistent, we averaged data from the previous and subsequent quarters. If states had more than one quarter of missing data, we allocated the difference between the last- and the next-reported quarter evenly over the missing quarters. Edited cases were cross-validated with other data sources when possible.
49 Email correspondence with CMS contact person for SEDS, on March 30, 2012.
50 Email correspondence with CMS contact person for SEDS, on March 30, 2012.