The number of Americans initially applying for unemployment aid fell to the lowest level in almost six years last week, the Labor Department reported Thursday. In the week ending Aug. 10, the advance figure of seasonally adjusted initial claims for jobless benefits fell by 15,000 to 320,000, the lowest since October 2007, from a revised figure of 335,000 for the previous week. The four-week moving average, which helps smooth out week-to-week volatility, declined by 4,000 to 332,000, the fewest since November 2007, and stayed well below the benchmark level of 375,000, which indicates a sustained recovery in employment. The advance figure of seasonally adjusted insured unemployment during the week ending Aug. 3 stood at 2.969 million, down 54,000 from the previous week. The U.S. unemployment rate edged down to 7.4 percent in July, the lowest since December 2008, but the economy added 162,000 jobs in the month, slightly fewer than the average monthly gain of 189,000 over the prior 12 months.