About every 7 years, FNS performs a nationally representative study (called a bookend study1) to examine the extent of error and abuse among food vendors authorized to accept WIC vouchers. The last bookend study was the 2005 WIC Vendor Management Study, which used fiscal year (FY) 2005 expenditure data to derive an estimate for 2004. Between bookend studies, there is a need to derive annual estimates of the level of improper payments for compliance with the Improper Payments Information Act of 2002. The purpose of the subsequent annual studies was to provide annual updates to the bookend studies using the developed aging methodology.