The following thoughts are based on The Pattern of the Chinese Past by Mark Elvin.
Many Chinese would perceive the Tang dynasty as the most prosperous period in the Chinese history. If measured in cultural diversity and openness to foreign countries, the Tang dynasty might be unrivalled. But a couple of important technological inventions and political innovations in the Song dynasty exerted long-lasting influence on the Chinese economy.
The invention of gunpowder provided the Song emperor with a greater capacity for invasion. Indeed, the dynasty was remarkably aggressive in conquering neighboring countries and regions. To fund the skyrocketing military expenses, some of the Song emperors printed so much money that inflation hurt people’s living standards. Woodblock printing, on the other hand, facilitated cultural exchange. In the Song dynasty, agriculture production was boosted because of improved grain seeds, advanced immigration techniques, and innovative farming arrangements (e.g. intercropping). Local officials as well as literati wrote about agriculture practices and the knowledge was promoted nationwide.
The improvement in transportation system (inland and ocean) during the Sui and Tang dynasties paved the development of interregional trade in the Song dynasty. The strong economic ties called for a united nation with uniform rules and regulations.