Cargill Inc., Archer Daniels Midland Co. and Bunge Ltd. accounted for 47 percent of 2007 commodities spending for aid, according to the U.S. Department of Agriculture. The program was created in the 1950s, partly to reduce domestic surpluses. The regulations require that almost all the peas, corn and other crops come from American sources, effectively steering the bulk of the business to the biggest food-trading companies. The rules also stipulate that 75 percent of the food must be transported on U.S.-flagged vessels, benefiting ship operators, including Liberty Maritime Corp., based in Lake Success, New York, and Sealift Inc., of Oyster Bay, New York. In 2007, the program’s shipping contracts were worth $385 million, according to the USDA.