Arlington, Va.—Ad spending on newspaper Web sites rose 31.5% last year to $2.70 billion, according to estimates released Wednesday by the Newspaper Association of America. Web site spending accounted for 5.4% of all newspaper ad spending in 2006. “We expect this upward trend to continue as publishers continue to capture a large and growing audience on the Web, and find these sources of revenues contributing more to the bottom line,” said John F. Sturm, president-CEO of the NAA, in a news release. Ad expenditures for newspaper Web sites increased 35% to $745.0 million in the fourth quarter, compared with the same period in 2005. NAA’s members represent 87% of the daily newspaper circulation in the U.S.