Over the past few years the prices of wheat, corn, rice and other basic foodstuffs have doubled or tripled, with much of the increase taking place just in the last few months. According to Paul Krugman, economist and New York Times columnist, a combination of long-term trends, bad luck,and bad policy can explain how this happened.
http://www.nytimes.com/2008/04/07/opinion/07krugman.html?_r=1&scp=5&sq=krugman&st=nyt&oref=slogin