- Kaphengst, Timo et al. Report to the European Commission, March 2011
Do the results tell the whole story? While a wide range of literature on the analysis of GM crop performance is available, empirical sensitivity analyses with regard to the potential limitations of available and comparable data were not widely applied. This study has aimed to generate a more complex picture on how different kinds of research methods, as well as other varying factors, may affect results on the economic performance of GM crops.
The assessment conducted in this study shows that the manner in which data is gathered (e.g. if a field trial or a survey was conducted) has an influence on the results. For instance, cotton yield data observed in field trials are generally lower, but gross margins are higher, than those observed in surveys. Differences in seed costs and pesticide costs between Bt and conventional cotton are higher in field trials than in surveys. In contrast, differences between GM and conventional cotton are lower for management and labour costs in field trials compared to results derived with surveys.
It could also be shown that the study conductor influences the performance estimates of GM crops. For example, higher yield advantages of Bt cotton are observed if private companies conducted the study when compared to studies conducted by public institutions (e.g. universities and governments).
Crop yields have a strong effect on the perception of the economic performance of GM crops as higher seed costs of GM crops often have to be compensated by more income from the crop itself, which can largely be achieved by higher yields. But yield levels in general depend upon a wide range of different factors which go far beyond the mere choice between GM and conventional crops. For example, this study demonstrated that the crop yields highly depend on the appropriate variety (no matter if GM or conventional) chosen by a farmer in relation to the weather and climatic conditions, under which the crop is grown.