Washington--Jan. 31--The U.S. economy finished 2000 on a weak note, expanding at an annual rate of only 1.4% in the fourth quarter, the slowest growth in more than five years. Economic expansion fell below the 2.2% growth in the third quarter, and it was dramatically slower than the 4.8% growth that marked the first quarter of 2000. Economists had expected growth of 1.9%.