Ling Liang Zhengzhou Information Engineering University   # 5, Jian-Xue Street # 5, Jian-Xue Street Wen-Hua Road Zhengzhou, Henan 450002 中国   liang_ling@163.com             JEL Areas: F4 : Macroeconomic Aspects of International Trade and Finance: General O1 : Economic Development: General