A paper published by Areal, Riesgo and Rodriguez-Cerezo in the Journal of Agricultural Science showed that genetically modified crops cultivated to date tend to perform better than their conventional counterparts as measured through yields, production costs and gross margins. In addition GM crops tend to perform better in developing countries as compared to developed countries, with Bt cotton being the most profitable crop grown to date.
The researchers conducting the study, who were at the time at the European Commission, Joint Research Centre (JRC) Institute for Prospective Technological Studies (IPTS), performed a quite sophisticated meta-analysis set of methods including Bayesian, semi-parametric and parametric approaches to the analysis.
This is quite an important effort as is summarizes results from a growing set of studies conducted over several crops, traits, and countries over several years.
F. J. Areal, L. Riesgo and E. Rodriguez-Cerezo. Economic and agronomic impact of commercialized GM crops: a
meta-analysis. Journal of Agricultural Science, Cambridge University Press 2012. doi:10.1017/S0021859612000111