Sung Agriculture and Commerce
During the late 8th and 9th centuries China's economy experienced a long period of dramatic changes. Prior to this time, the vast amount of the Chinese population and wealth had existed on the great Hopei-Honan plain. However, the population was now shifting to the south into the Yangtze Valley. In the Yangtze Valley farmers found soil that was much more fertile, and as a result they began producing large surpluses. The surplus led to more trade, larger populations, a new merchant class, and the rise of new towns. However, by 830 AD, the Yangze Valley would suffer one natural disaster after another, including insect invasions, floods, and droughts.