The major reason that so much corn is grown in Illinois is
that the soils and weather are very well suited to the crop,
and as a result yields are high. Figure 2.1 shows yield
trends for corn and other major Illinois field crops over
the period 1990 through 2008. Corn yields have increased
by 2.6 bushels per year over that period, or a total of more
than 45 bushels, or some 30%. There are few places in
the world, and none without extensive irrigation, that can
point to such high productivity for any crop. In 2007, the
average U.S. yield was nearly twice the world average
yield, and the average Illinois yield was about 15% higher
than the U.S. average yield. Illinois produces about 17% to
18% of the U.S. corn crop, and more than 7% of the corn
produced in the world.