WASHINGTON — A recent study by the Economic Research Service at the U.S. Department of Agriculture and University of California, Davis examined the difference in prices of products sold under the Special Supplemental Nutrition Program for Women, Infants and Children (WIC) at small retail stores compared to higher retail stores. The findings discovered that smaller retailers charge higher prices than large retailers for comparable WIC products.

The study, which was published in the September issue of Amber Waves, used redemption data in California from 2009-12 to examine patterns in WIC redemptions and costs. The researchers discovered that one of the most popular packages, which consists of a dozen eggs, a gallon of low-fat milk, a pound of cheese, and either peanut butter or a pound of dried beans, peas or lentils, had a median redemption value of $20.05 at retailers with one or two registers, while large supermarkets with at least 10 registers charged a median redemption value of $12.95.

But prices did not drop steadily as store size went down. Retailers with three or four registers had significantly lower prices than smaller stores, and while retailers with five or six registers dropped slightly, their prices were comparable to retailers with at least five registers.

Restricting WIC redemptions to large supermarkets may solve this issue, but smaller stores represent only a small portion of WIC sales, making potential savings limited, the study said.

The Special Supplemental Nutrition Program for Women, Infants and Children (WIC) is U.S.D.A.’s third largest food assistance program, providing vouchers, checks, or electronic benefit transfers for specific packages of food at WIC-authorized retailers. The program issued to an average of 8.7 million women, infants and children per month in 2013. WIC is funded annually by congressional appropriations, making the program’s capacity dependent upon the funding level and costs per participant, which depends in part on the prices of the products. The retailers would be reimbursed by the states for the items sold to WIC participants.