(2) Commercial prosperity in the Song Dynasty, with unprecedented domestic and foreign trade activity.

(3) Reason: War in the north and relative peace and stability in the south. The migration of population to the south has brought sufficient labor force, advanced production technology and production tools to the south.

(4) Understanding: Strengthening regional economic exchanges can promote economic development; A peaceful and stable social environment is conducive to economic development; The increase of labor force and the improvement of workers' quality are beneficial to economic development.