By John S. McClenahen After increasing in both March and April, the U.S. Labor Department's import price index was unchanged in May. A modest increase in petroleum prices was offset by a slight decline in prices for imports of non-petroleum items, says the department's Bureau of Labor Statistics (BLS). Meanwhile, influenced by declines in agricultural prices and prices for computer peripherals and other capital goods, the U.S. export price index fell 0.1% in May. Export prices had risen in both March (0.3%) and April (0.4%). In May, both the import-price and export-price indexes were below economists' expectations. Economists anticipated a 0.4% rise in import prices and a 0.2% increase in export prices. Most dramatic on the import-price side in May was the behavior of petroleum prices. The BLS' index for petroleum imports rose only 0.9% last month, following a 17% increase in March and a 12.7% increase in April.