As an outcome measure in intervention trials, the finely grained risk score is more sensitive than the trinary risk classification. The additional clinical value of the risk score relative to the categorical measure needs to be determined.

Background: Although Medicaid is a federalprogram, it is administered primarily by the states. Enrollees move from state to state, but their migration patterns have remained largely unknown. There are concerns about the possibility of enrollment gaps, lack of health insurance coverage, breaks in continuity of care, unmet need, risks to health status, and increased system-wide costs due to uncompensated care and the use of higher cost emergency room services because of enrollment gaps. There is also concern about the extent to which people enrolled in more than one state are double counted.Objective: To examine the migration of Medicaid enrollees across states. We use 2005We use -2007 Medicaid enrollment records that were unduplicated and linked across states and over the study period. We report descriptive statistics on enrollee migration across states. Methods:Results: Among all enrollees, 3.7 percent moved to another state at least once and most moved only once. Overall, 72.2 percent of moves did not result in an enrollment gap, whereas 8.2 percent of moves resulted in gaps of fewer than three months, and 11.4 percent of moves resulted in gaps of more than six months. Conclusions:

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