Sources of Increased Instability in Indian and U.S. Cereal Production
分解印度和美国谷物生产标准差增长的原因，发现州际和作物间产量协方差显著上升，主要源于产量波动增大和州际产量抵消模式减弱，可能与价格波动、高产技术及遗传基础狭窄有关。
Abstract Recent growth in Indian and U.S. cereal production has been accompanied by a more than proportional increase in the standard deviation of production. This study applies variance decomposition procedures to state data on crop production to analyze the sources of this increased instability. It is found that production has become significantly more covariate between states and crops, largely because of increased yield variability and a loss in offsetting patterns of variation between crop yields in different states. These changes may be associated with more variable prices, with higher‐yielding technologies, and with a narrowing of the genetic base.