A large number of factors have contributed to the higher prices of corn and other commodities over the past year.

The beginning of the price increase can be traced to the USDA's forecast of 2010 corn planted acreage and the estimate of June 1 corn stocks released on June 30, 2010, said University of Illinois agricultural economist Darrel Good.

"The USDA's June 2010 forecast of corn planted acreage came in at 87.872 million acres, 926,000 fewer than indicated in the March 2010 Prospective Plantings report. The market was generally expecting acreage to exceed March intentions," he said.

The final planted acreage estimate for 2010 was 320,000 acres larger than the June forecast. Area harvested for grain was 441,000 acres larger than was forecast in June, but declining yield prospects more than offset the slightly larger acreage estimates.

The USDA's estimate of June 1, 2010, corn inventories was about 300 million bushels — or 6.5 percent — smaller than was anticipated by the market and about 245 million bushels smaller than our pre-report calculation.

"The low stocks estimate implied a level of feed and residual use during the third quarter of the 2009-10 marketing year that was too large to be believed. Subsequently, the Sept. 1, 2010, corn stocks estimate came in larger than expected so that feed and residual use of corn during the final quarter of the year appears abnormally small," he said.

The estimates of feed and residual use for the last half of the year and for the entire year appear logical, but the distribution between the third and fourth quarters was unusual.

"A year later, there is once again a major focus on the USDA's Grain Stocks and Acreage reports to be released on June 30.

"For the June 1 stocks estimate, it is useful to calculate what the inventory should have been based on the estimate of March 1 stocks, known consumption in March, April and May (domestic processing uses and exports) and an estimate of feed and residual use during the quarter.

“Based on weekly USDA estimates and Census Bureau estimates for March and April, exports during the March-May quarter were near 504 million bushels,” Good said.