The Influence of Genetic Modification Technologies on U.S. and EU Crop Yields

A second problem occurs if one assumes a priori that yield trends are linear. Because of adoption rates and learning processes, nonlinear functional forms could be more relevant for approximating changing yield trends. While the EU corn yield trend was only about 0.5 bu/year less than the U.S. trend prior to 1996, the EU trend line has been almost 1 bu/year less since 1996. Because technological change is often gradual and influenced by learning processes, the EU corn yield slope change indicated by the parameter estimates of equation (2) is likely more gradual than that indicated by a binary shift variable. [...]it does not appear that differences in environmental policies related to nitrogen fertilizers can explain the differences in corn yield trends over the past 2 decades. Weed control in soybeans, however, was more difficult prior to GM technologies because selective broadleaf herbicides were only partially effective (Perry, Moschini, and Hennessy, 2016). [...]if GM technologies increase crop yields, it would likely be more apparent in crops for which traditional methods of weed control had lower efficacy.

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