A sharp drop in crude oil prices in the past month is finally showing up at U.S. gasoline pumps. The national average price of a gallon of regular gas has fallen from $1.72 on March 14 to a $1.60, according to data compiled by AAA. John C. Felmy, chief economist for the American Petroleum Institute, said prices may fall more because the full extent of the drop in oil prices has not yet been fully reflected at the pump, according to the Washington Post. Crude oil accounts for 40 to 50 percent of the price of a gallon of gasoline. When crude moves up or down by $1 a barrel, the price at the pump typically changes by 2.4 cents a gallon, according to the Post. John H. Lichtblau, chairman of the Petroleum Industry Research Foundation in New York, said the national average price could drop below the federal government's summer prediction of $1.56 a gallon, the Post said.