In 2006, FNS asked the Institute of Medicine to review the WIC food packages. The IOM proposed major changes to improve nutrition and encourage breastfeeding but also expressed the concern that changes related to partial breastfeeding may have unintended consequences. The IOM recommended that FNS conduct an impact study evaluating the birth month breastfeeding changes to the WIC food packages. 

The WIC Participant and Program Characteristics (PC 2006) report summarizes demographic characteristics of WIC participants nationwide in April 2006, along with information on participant income and nutrition risk characteristics. A national estimate of breastfeeding initiation for WIC infants is included. The report also describes WIC members of migrant farm-worker families.

In 1991 and 1998, FNS conducted national studies of WIC vendors to determine the extent of vendor violation of program rules. After the 1998 study, FNS issued regulations to correct vendor practices. The 2005 study replicates the 1998 study to determine whether the regulations were effective, and to measure the frequency of vendor violations and the degree to which vendors charge accurate prices for WIC transactions.