Wheat aphids and the damage they cause are examined at the County Agro-technological Extension Centre at Shuangliu, Sichuan Province. - - General: General. China's increased economic activity in recent years has led to a revitalization of the market place and enabled both collectives and individuals to increase their income. Free markets in both urban and rural areas have enjoyed booming business since the state relaxed controls on the prices of pork, fish and vegetables, earlier in 1985. Transactions in free markets rose to more than 13 million Yuan in the first quarter of 1985, an increase of 2.5 billion over the same period in 1984. It is estimated that by the end of 1985, figures could reach 55 billion Yuan; a rise of 20% over last year. Free markets, supplying a variety of commodities such as grain, meat, aquatic products, building materials, furniture, birds and flowers, have become an "indispensable channel" for commodity circulation. In addition, the economy has been greatly strengthened by improved agricultural techniques such as the utilization of the by-product of biogas production for power and fertilizer.