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.

The Prime Vendor Pilot was conducted as part of USDA's Business Process Re-engineering efforts to improve the administration and operation of the Food Distribution Program on Indian Reservations. Under this pilot, USDA partnered with the Department of Defense, which had an existing contract with commercial vendors and distributors.