美国粮食价格突变及其对国内农业安全的启示

The Mutation of U. S. Grain Prices and Its Enlightenment on China's Agricultural Safety

美国粮食市场价格突变可能为我国农业安全带来不可估量的冲击。以玉米和大豆产业为例,选取2000—2013年季度价格相关数据,基于PPM模型识别了玉米和大豆价格突变节点并测算其形成原因。实证结果显示,自21世纪以来,全美玉米市场共发生了六次价格上升突变、两次价格下降突变;大豆市场则历经四次价格上升突变、两次价格下降突变。粮价突变是供需因素与国际贸易、原油价格、美元指数变动等众多非供需因素共同作用的结果,因所处政治经济背景不同,各阶段形成原因也不尽相同。分析表明,美国粮价突变首先通过价格信息与贸易渠道间接的影响国内玉米和大豆价格;然后经由其他农产品价格波动、短期供给波动、国际游资及外商控制等路径对国内农业安全带来威胁。

American grain price structural mutations may bring immeasurable impact for China ’ s agricul-tural security .Using corn and soybean industry as examples , this paper selects quarter price data from years 2000 to 2013, and uses PPM model to identify price mutation points and calculates the probabilistic and posterior mean.The empirical results show that since the 21st century, there are six times up struc-tural mutations and two down structural mutations for corn prices , while there are four times increased structural mutations and two down structural mutations for soybean prices .The agricultural commodities price structural mutations are outcome of combined action of supply and demand factors and other factors , such as international trade , the price of crude oil , the dollar index , etc.Because of different political and economic background , the reasons for the formation of each stage are different .In-depth analysis shows that the U.S.corn and soybean market price structural mutations affect the price of the domestic market , through the price information channels and trade channels .Then it brings threat to China ’ s agri-cultural security through other agricultural price volatility , short-term fluctuations in supply , international hot money, foreign control path, etc.