No domestic priority preoccupies China's leaders more than preventing a collapse of its rural economy. Alarmed by the idea of hundreds of millions more workers flooding into cities in search of jobs, and the threat they could pose to social and political stability, they have striven to discourage a mass exodus from the countryside.

Their efforts have partly succeeded. Thanks to agricultural reforms in the 1980s, rural productivity and incomes have risen steadily. China is the world's biggest consumer and producer of many foods. Although it has recently become a net food importer, it has successfully expanded exports of premium products such as horticulture.