The MAX and its source data -- the Medicaid Statistical Information System (MSIS) -- are the primary sources of information about each of the more than 50 million people enrolled in Medicaid each year. CMS produces both MSIS and MAX and makes them available publicly (with a data use agreement) for research purposes. Because Medicaid is the largest insurer of LTSS in the United States, these data provide the most detailed information currently available about people using LTSS services nationally.
Most MAX data are derived directly from MSIS. MSIS contains FY Medicaid enrollment and claims-paid information for each state and the District of Columbia. The MAX data system is a cleaned and enhanced version of MSIS that enables analyses of enrollment, utilization, and expenditures at the person level. Unlike MSIS, which reflects claims as of the date they were paid, MAX includes the services used by Medicaid enrollees during a calendar year.
We used the MAX PS files for 2009 for the analyses presented in this report. The MAX PS files are person-level files that contain information on enrollee demographic and eligibility characteristics and summary information on claims paid for services used by each enrollee during the year. Summary expenditure information in the MAX PS file is disaggregated by type of service.