"Using the 2004 corn price of $2.06 per bushel as a reference, actual corn prices increased by an average of $1.65 per bushel from 2006 to 2009. Only 14 cents (8%) of this increase was due to ethanol subsidies. Another 45 cents of the increase was due to market-based expansion of the corn ethanol industry. Together, expansion of corn ethanol from subsidies and market forces accounted for 36% of the average increase that we saw in corn prices from 2006 to 2009. All other market factors accounted for 64% of the corn price increase." Read more here.
The Impact of Ethanol and Ethanol Subsidies on Corn Prices: Revisiting History
by Bruce A. Babcock and Jacinto F. Fabiosa. Center for Agricultural and Rural Development. Iowa State University.