基金This paper was prepared for the 25th International Conference of Agricultural Economists, August 16-22, 2003, Durban, South Africa. This project is financed by the National Natural Science Foundation of China (70173016) and Shanxi Province Soft Science Research Program (011002). During the research, we have obtained the full support of Shanxi Province, Zhejiang Province and National Rural Fixed 0bservation Network 0ffice. We hereby show our thanks to all of them.