The Role of Weather in the Pattern of Corn Prices over Time
June 14, 2017
Scott Irwin, Darrel Good, and Todd Hubbs
In the farmdoc daily article of June 7, 2017, we examined the long-term pattern of corn prices during the era spanning from 1973 through November 2006 and the new era that began in December 2006. We concluded that: (1) there is a long-run average nominal price of corn for different eras that tends to emerge fairly early in each era; (2) corn prices revert to the average within each era; and (3) the deviations and reversions to the average price do not occur in a predictable cycle in terms of either magnitude of deviations or duration of the deviations. In other words, we argue that long-run crop prices have a stable average within a defined era and adjust to supply and demand shocks in a classic cobweb fashion. However, the price adjustments do not follow the repetitive cyclical pattern of the classical cobweb model, but rather are highly volatile and difficult to forecast due to the substantial variation in supply and demand shocks over time and the exact market reaction to those shocks.