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 study is part of a larger FNS effort to ensure WIC program integrity and to comply with the Improper Payments Information Act of 2002 which requires FNS to estimate improper payments in its programs.

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.