WASHINGTON (AP) — U.S. consumer prices edged down in August, the first monthly drop since the spring of 2013, as gasoline, airline tickets and clothing prices all fell. Ian Shepherdson, chief economist at Pantheon Macroeconomics, said that the drop in prices would give a "powerful boost" to "doves" on the Fed, officials who argue that at the moment unemployment and weak economic growth are bigger problems than the threat of future inflation. The recent decline in gasoline prices is one reason that economists are optimistic that consumer spending will show solid gains in the coming months. [...] some critics say the Fed needs to start raising rates in coming months to make sure its prolonged period of easy credit policies does not set the stage for future inflation problems.