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.

The purpose of the study was to learn the extent to which retail grocers, defined as "vendors" in the WIC Program, authorized to provide food to WIC participants, were violating program rules and procedures, and to determine which programmatic and/or demographic variables could be associated with vendor violations.