It took almost 1,000 years for wheat yields to increase from 0.5 to 2 metric tons per hectare. In contrast, from 1940 to 1980 the yield for wheat increased from 2 metric tons to over 6 metric tons per hectare. These are big numbers, and they had a big effect on developing countries where large parts of the population were able to surplus food for the first time. Still, critics have argued that...