Generally, technologies are judged on their net benefits, not on the claim that they are harmless: The good effects of, say, the automobile and aspirin outweigh their dangers. Today, arguably, adopting certain new technologies is harder not just because of a policy of precaution but because of a bias in much of the media against reporting the benefits.

Shale gas is one example, genetically modified food another, where the good news is deemed less newsworthy than the bad. A recent French study claimed that both pesticides and GM corn fed to cancer-susceptible strains of rats produced an increase in tumors. The study has come in for withering criticism from mainstream scientists for its opaque data, small samples, unsatisfactory experimental design and unconventional statistical analysis, yet it has still gained headlines world-wide. (In published responses, the authors have stood by their results.)

The French study contradicts a Japanese paper that used larger samples, longer trials and accepted experimental designs, yet received virtually no notice because it found no increase in cancer in rats fed on GM crops. This is a problem that's bedeviled GM technology from the start: Studies that find harm are shouted from the media rooftops, those that do not are ignored.

So to redress the balance, I thought I'd look up the estimated benefits of genetically modified crops. After 15 years of GM planting, there's ample opportunity—with 17 million farmers on almost 400 million acres in 29 countries on six continents—to count the gains from genetic modification of crop plants. A recent comprehensive report by Graham Brookes and Peter Barfoot for a British firm, PG Economics, gives some rough numbers. (The study was funded by Monsanto , which has major operations in biotech, but the authors say the research was independent of the company and published in two peer-reviewed journals.)

The most obvious benefit is yield increase. In 2010, the report estimates, the world's corn crop was 31 million tons larger and the soybean crop 14 million tons larger than it would have been without the use of biotech crops. The direct effect on farm incomes was an increase of $14 billion, more than half of which went to farmers in developing countries (especially those growing insect-resistant cotton).