NEW YORK (Reuters) - U.S. average gasoline prices rose 8 percent, or 21 cents, in 2007 from the prior year, an industry analyst said, as oil prices rose. The average annual price for U.S. gasoline was $2.7878 in 2007, up from 2006's $2.5730, according to the Lundberg survey of about 7,000 U.S. gas stations.