Washington--Jan. 4--The number of American workers filing new claims for unemployment benefits jumped last week to its highest level since July 1998 as the U.S. economy continued to slow. First-time claims for state unemployment insurance jumped 16,000 to 375,000 during the week ended Dec. 30, the Labor Department said. Separately, the Commerce Department reported that factory orders rose 1.7% in November, boosted by a jump in orders for transportation equipment.