There’s a new paper out on genetically-engineered corn. Its results?:
This paper sought to identify whether, in fact, for corn “the nation-wide data . . . in the United States do not show a significant signature of genetic-engineering technology on the rate of yield increase,” as was indicated by NASEM (2016). Using corn yield panel data corresponding to roughly 28,000 U.S. county-years before and after adoption of GE corn, a simple model only including a time trend confirms NASEM’s assertion, as the effect of GE adoption appears, if anything, to have had a negative effect on yields. However, subsequent analysis reveals this simple model is biased. After controlling for weather and soil characteristics, and assuming a homogeneous effect of adoption, we find that adoption of GE corn has led to an approximate 17 percent increase in corn yields. We also find significant heterogeneity in the yield-effect that is not related to state-boundaries but rather to soil characteristics. On average, adoption of GE corn has led to an 18.5 bushel per acre increase in yield, but the effects range from 12.5 to 25.1 bushels per acre depending on soil characteristics. We conjecture that the variation across soil types may be related to differences in insect pressure.
While we found important soil-GE adoption interactions, there were no significant interactions related to weather. The findings suggest that the current GE traits have not led to more resilience to heat or water stresses. Moreover, while we find that the variance in corn yield has increased over time, adoption of GE corn has not lowered the variance. Nonetheless, if as our results show, adoption of GE corn increases yield without affecting variance, the coefficient of variation on yields has fallen as a result of GE corn adoption. This suggests GE corn is less risky as, for example, the actuarially fair price of insurance to indemnify a given yield falls as the coefficient of variation falls (pgs. 21-22).
So, once again, maybe we should calm down about GMOs.