The conception, selection and implementation of medium-large investment projects in agriculture often suffer from a lack of serious economic analysis assessing the validity, rationality and viability of the projects. Cost-benefit methodologies, so widespread in other economic sectors,1 are much less applied in agriculture.2 Instead, and especially in many developing countries, investments in agriculture are justified on the basis of some political objectives, lobbying, unfunded distributional concerns, vaguely defined environmental benefits and a misguided interpretation of food security (which is often thought as equivalent to self-sufficiency in food production).