Nissan Motor Co. achieved the highest assembly productivity in North America for the seventh straight year in 2000, with its assembly hours per vehicle falling 7.1 percent from a year earlier to 17.4 hours, a U.S. research firm said Thursday.

Honda Motor Co. ranked second, with its assembly hours per vehicle standing at 19.9 hours, followed by Toyota Motor Corp. at 21.6 hours, according to Harbour and Associates Inc.

The ranking of the top three was unchanged from 1999, showing the competitive edge of Japanese automakers.

The data for General Motors Corp. came to 26.8 hours, 9.4 percent less than in 1999, and closing in on Ford Motor Co.'s 25.7 hours, up 2.8 percent, the firm said.

While it took GM 31.6 hours to produce a car in the fourth quarter of 1997, 6.7 hours behind Ford, Harbour and Associates said GM's efforts to improve productivity during the past few years are gradually bearing fruit.