Towards the end of the first millennium, the importance of rice grew in the country as a whole.28 From the Tang Dynasty onwards, northern China was beset by droughts and harassed by northern nomads. Meanwhile, new long-grained varieties of rice from Vietnam allowed southern farmers to plant two crops a year, while farming innovations enabled higher yields. The southern population boomed and the southern economy prospered; rice surpluses filled the coffers of the state. China’s centre of economic gravity moved southwards from the depleted north, never to return.
