WASHINGTON - Fewer Americans than anticipated filed claims for jobless benefits last week, signaling the worst employment slump in the post-World War II era is easing as the economy expands. Initial unemployment claims fell by 12,000 to 502,000 in the week ended Nov. 7, the lowest level since January, Labor Department figures showed today in Washington. The number of people receiving jobless benefits dropped, as did those getting extended payments. The four-week moving average of claims, a less volatile measure, decreased to 519,750, the lowest level in almost a year, from 524,250 (see top chart above).