SUMMARY: The present paper presents a meta-analysis of the economic and agronomic performance of genetically modified (GM) crops worldwide. Bayesian, classical and non-parametric approaches were used to evaluate the performance of GM cropsv.their conventional counterparts. The two main GM crop traits (herbicide tolerant (HT) and insect resistant (Bt)) and three of the main GM crops produced worldwide (Bt cotton, HT soybean and Bt maize) were analysed in terms of yield, production cost and gross margin. The scope of the analysis covers developing and developed countries, six world regions, and all countries combined. Results from the statistical analyses indicate that GM crops perform better than their conventional counterparts in agronomic and economic (gross margin) terms. Regarding countries’ level of development, GM crops tend to perform better in developing countries than in developed countries, with Bt cotton being the most profitable crop grown.

Law 46/1999 incorporated formal water markets into the Spanish legal and regulatory framework, allowing spot water markets and the creation of water banks. The implementation of water markets in Spain aimed at improving the efficiency of water use by reallocating water towards uses with higher added value. However, the performance of water markets in Spain has been rather disappointing, since they have been operative only during drought periods, and even under these extreme scarcity situations, trading activity counted for less than 5.0% of total water use. The narrowness of the market suggests that there are some barriers hampering their effective functioning. This paper examines the evolution and performance of water markets in Spain, relying on a transaction costs analysis framework. This analysis allows the identification of the main factors impeding water markets from operating effectively as a water reallocation tool. This analysis also provides some guidelines on how to overcome these obstacles and, thus, how to improve the efficiency of water use.