L24-33中的两句话，反复读了好多遍，就是不理解是什么意思，也无法将其与原文联系，希望NN们指点
In 1910 over 600,000 Black workers, or then percent of the Black work force, reported themselves to be engaged in "manufacturing and mechanical pursuits," the federal census category roughly encompassing the entire industrial sector. The Great Migration could easily have been made up entirely of this group and their families. It is perhaps surprising to argue that an employed population could be enticed to move , but an explanation lies in the labor conditions then prevalent in the South. | 
