Purdue’s Philip Abbott says that prior to a 2007-08 spike in commodity prices, the U.S. exported well over half of the corn that entered international markets. But since then he says high corn prices have caused the rest of the world to expand their production and become more self-sufficient.

Abbott notes that about 40 percent of the corn grown in the U.S. is used for ethanol production to comply with a federal standard.

Although American farmers have shifted acreage away from other crops and into corn, he says the U.S. hasn’t kept up with other nations such as those in South America which have significantly increased their corn acreage in recent years.