ByJohn S. McClenahen Although some companies continue to trim their workforces, mass layoffs in manufacturing last month declined dramatically. The number of employer layoffs involving at least 50 people from a single company fell to 240 in February from 848 in January, the U.S. Labor Department reported March 24. Last month a total of 23,043 workers were affected by layoffs, down from 89,551 affected in January. The manufacturing sector of the U.S. economy accounted for 26% of all mass layoffs in February, the smallest share for any February on record, the Labor Department says.