Corn yields in the Corn Belt have been increasing steadily, with the state average yield in Illinois rising at a rate of 1.9 bushels per acre per year from 1970 to 2009, but 3.6 bushels per acre per year since 1996. With few exceptions, the weather during the past 15 years has been very favorable for corn. But improvements in hybrids and in management have played an important part in these yield increases as well.