A 2009 report from Union of Concerned Scientists. Excerpts:
For years the biotechnology industry has trumpeted that it will feed the world, promising that its genetically engineered crops will produce higher yields. That promise has proven to be empty, according to Failure to Yield, a report by UCS expert Doug Gurian-Sherman released in March 2009. Despite 20 years of research and 13 years of commercialization, genetic engineering has failed to significantly increase U.S. crop yields....
The report recommends that the U.S. Department of Agriculture, state agricultural agencies, and universities increase research and development for proven approaches to boost crop yields. Those approaches should include modern conventional plant breeding methods, sustainable and organic farming, and other sophisticated farming practices that do not require farmers to pay significant upfront costs. The report also recommends that U.S. food aid organizations make these more promising and affordable alternatives available to farmers in developing countries.
Source: Union of Concerned Scientists