What's the difference between Jiangnan described in the Book of Song Dynasty and the Book of Han Dynasty? The reason for this change.

Hanshu reflects the backwardness of Jiangnan economy in Han Dynasty, while Songshu reflects the great development of Jiangnan economy in Southern Dynasties, even surpassing the North in many places (or Jiangnan economy changed from poverty and backwardness to prosperity). Impact: The development of the south of the Yangtze River has had a far-reaching impact on the economic structure of China, laying the foundation for the economic center of gravity to move south.

As Song Shu said, people from the north moved south, and advanced technology from the north was promoted in the south. In addition, northerners have increased the labor force in the south, and a large amount of cultivated land has been utilized and developed, making the country rich and the people safe.

Historical Records was written by Sima Qian in the Western Han Dynasty. At that time, the production technology in the south was still very backward, so when there were clouds, people could have enough to eat, but there were no rich people.