Pierre-Alain Jayet

An incentive approach to land set-aside programs

Abstract This paper is devoted to a theoretical analysis of policies aiming at reducing the supply of agricultural produce through contractual or mandatory land set-aside. The model relies on contract theory under adverse selection: it allows us to evaluate the impact of asymmetric information about yields on the optimal price support policy and on land set-aside. Specifically, we analyze an optimal contractual policy consisting of a subsidy system which makes transfers dependent on the set-aside area and a policy of mandatory land set-aside applying uniformly to all farms and ignoring incentive constraints. Numerical simulations allow us to assess and compare the respective effects of these policies.

Evaluating the Efficiency of a Uniform N-Input Tax under Different Policy Scenarios at Different Scales

Nitrate pollution from agriculture is an important environmental externality, caused by the excessive use of fertilizers. The internalization of this problem, via a tax on mineral nitrogen, could lead to a second best solution, reducing nitrate emissions. Several authors suggest that a reduction in agricultural support could produce similar results. In this paper, we examine the effects of different levels of a uniformly implemented nitrogen tax in France under two policy scenarios, corresponding to post Agenda 2000 and 2003 Luxembourg reforms of European Union’s Common Agricultural Policy, in order to reveal the synergies and conflicts between the tax and the policy scenarios in terms of nitrate emissions abatement. The analysis is performed at different geographical scales, from the national to the regional and is based on a bioeconomic approach that involves the coupling of the economic model AROPAj with the crop model STICS. Results show that the efficiency of the N-tax varies according to the geographical scale of the analysis and the type of farming. Furthermore, we prove that a uniform implementation may lead to perverse effects that should always be taken into account when introducing second-best instruments.

How Cost-Effective is a Mixed Policy Targeting the Management of Three Agricultural N-pollutants?

This paper assesses the cost-effectiveness of a mixed policy in attempts to reduce the presence of three nitrogen pollutants: NO 3, N 2O, and NH 3. The policy under study combines a tax on nitrogen input and incentives promoting perennial crops assumed to require low input. We show that the mixed policy improves the cost-effectiveness of regulation with regard to nitrates, whereas no improvement occurs, except for a very low level of subsidy in some cases, for gas pollutants. A quantitative analysis provides an assessment of impacts in terms of land use, farmers’ income, and nitrogen losses throughout France and at river-basin scale.

Estimating the Marginal Social Value of Agriculturally Driven Nitrate Concentrations in an Aquifer: A Combined Theoretical-Applied Approach

We combine a theoretical model and a quantitative modeling chain based on a bio-economic model and a hydrological model in order to assess the marginal damage related to the nitrate concentration in an aquifer. The fundamental concept is to take the steady state level resulting from a social planner’s optimization program as the target level of nitrate concentration. The interest of doing this is three-fold: (i) we characterize the social value of damage related to the targeted nitrate concentration; which (ii) leads us to design the optimal path consistent with the target; and (iii) we can in turn assess welfare losses arising when the tax path deviates from the optimal one.

Retrait des terres et subsidiarité dans le cadre de la Politique Agricole Commune

Ce papier aborde la question de la subsidiarite dans le cadre de la Politique Agricole Commune. Linstrument privilegie est ici un contrat de gel de terre dont la definition releve soit directement des instances de lUnion Europeenne, soit des instances nationales. Dans ce dernier cas, dit de subsidiarite, le budget public associe aux contrats est supporte par les budgets nationaux. Les contrats sont determines dans les deux types dintervention publique, nationale et europeenne. Dans le cas dune politique de subsidiarite, les contrats nationaux sont definis par un equilibre de Nash resultant dun jeu intra-europeen. On ne peut determiner analytiquement la politique qui domine lautre en terme de welfare, sauf dans le cas tres particulier dEtats « identiques ». Dans ce cas, la politique commune domine la politique de subsidiarite. Toutefois le cadre theorique elabore est propice a lanalyse empirique. Pour illustrer cette demarche, une analyse quantitative est proposee pour le secteur du ble tendre dans lUnion Europeenne a 12 selon des donnees de 1994. Elle permet la comparaison des gains pour les producteurs, les consommateurs, et les contribuables des 12 pays dans les 3 situations offertes successivement par letat de reference, la politique commune de gel de terre et la politique de subsidiarite.

Représentation d'un secteur de production agricole multi-producteurs. Une méthode pour l'estimation des charges variables par culture

[eng] A set of models is proposed in order to estimate the effects of the measures of the CAP on the French crop supply. The modelling of the behaviour of each producer group needs a lot of data which are available after using some estimation tools and raw data. [fre] Dans la logique du travail de modelisation engage sur le secteur francais de la production vegetale, le probleme de lalimentation du modele en donnees est entierement reconsidere. Les premiers resultats sont presentes en matiere devaluation de limpact sur loffre des instruments de la PAC.