The purpose of this study is to evaluate the effectiveness of state agencies current peer group systems, and to provide guidance to state agencies on how to evaluate and update their systems. Specifically, it uses empirical analysis to identify one or more effective models for establishing vendor peer groups that could apply to most state agencies.

This report provides improper payment estimates for fiscal year 2011 using a methodology for “aging” the 2005 bookend study. The methodology yields nationally representative estimates of the number of vendors that over- and undercharged and the amount of over- and undercharges across all WIC vendors.

This report provides improper payment estimates for FY 2010 using a methodology for “aging” the 2005 bookend study. The methodology yields nationally representative estimates of the number of vendors that over- and undercharged and the amount of over- and undercharges across all WIC vendors.

This report provides improper payments estimates for FY 2009 using a methodology for “aging” the 2005 bookend study. This updates previous reports providing estimates from 2005 to 2008.