A jump in corn prices at the end of October may have been due to speculations about a possible change in Chinese export policy.

The increase came after the harvest of an unusually large corn crop.

“The main reason for the increase in corn prices was speculation that China is changing its policy toward corn exports,” said Robert Wisner, ISU Extension economist and professor in economics.

Wisner said China has been a net exporter of corn since the 1970s.

“There has been speculation over the last decade that at some point China would go from being a net exporter to a net importer,” he said.

Some experts believed that a shift may occur this year, he said.

“China may be in the process of reducing its exports for the year ahead,” Wisner said. “The current estimate is that China’s corn crop was down from last year.”

Wisner said the U.S. market would be sensitive to a change in Chinese export policy because “any shift of a major exporter toward reduced export would shift additional demand to U.S. corn.”

Estimates for China’s corn crop have been taken from the USDA’s Oct. 12 report.

Wisner said predicting China’s corn production from the USDA October report is hard to do.

“There has been a very strong tendency to underestimate Chinese corn exports based on the USDA October report,” he said.

Neil Harl, distinguished professor of economics and agriculture, said trade signals are used to predict market change and estimating changes in the market is difficult.

“There’s always a fair amount of speculation in commodities markets,” he said.

Harl said China is now one of the “worldwide players” in corn production because it is a large source of demand and it also produces a great deal of corn.

Wisner said the increase in corn prices from Oct. 22 to Oct. 29 was unexpected because farmers have been harvesting a large corn crop.

“This year farmers are harvesting the largest corn crop on record nationally. Large corn crops normally mean lower prices,” he said. “Most analysts had anticipated this would be a year of relatively low corn prices.”

Harl said corn prices decreased late last week and the possibility of China shifting from a net exporter to a net importer this year appears unlikely.

Adjusted figures for China’s corn production will be part of a new USDA report to be released Wednesday morning.