A May 2008 report from USDA on recent rises in commodity prices, while emphasizing the greatly increased demand from developing countries as well as the decreased supply because of adverse weather in parts of the world, comments (p. 18):

 ”The data suggest that while U.S. corn used for ethanol production had only

a small effect on global markets in the 1980s and 1990s, the increase in U.S.

ethanol production over the past 5 years and the related significant changes

in the structure of the U.S. corn market have had a more pronounced impact

on the world’s supply and demand balance for total coarse grains recently.

Importantly, since the United States is the world’s largest corn exporter,

some of the higher prices resulting from increased U.S. demand has spilled

over onto world markets.”