4 présentations

• 
  09h00 - 09h25

  Competition between different groundwater uses under a regime shift

  • Julia de Frutos Cachorro, prés., University of Barcelona
  • Jesús Marín-Solano, Universitat de Barcelona, BEAT
  • Jorge Navas, Universitat de Barcelona, BEAT

  We study the impact of shocks in a common groundwater resource problem using a differential game. In particular, we extend the work made in de Frutos Cachorro et al. (Environmental and Resource Economics, 2018) for the case of asymmetric players. Different players correspond to different groundwater uses (e.g. agriculture, industry, drinking water etc...), which enable us to consider competition between economic sectors for the limited available stock. We also analyse different types of asymmetries between water users, such as different water demands, discount preferences and/or groundwater costs. The shock is deterministic and consists of a sudden change in the dynamics of the resource, namely a decrease in the recharge rate of the aquifer. Such a shock can happen because of an exceptional extraction of water, intended for instance for the filling of a new reservoir or for water needs of a new residential area. We compare subgame perfect cooperative and non-cooperative solutions. Finally, we conduct a numerical analysis in order to illustrate the results.

• 
  09h25 - 09h50

  Mobile natural resources and conflict

  • Nicolas Querou, prés., CNRS & CEE-M

  Building on a simple model allowing for endogenous extraction activities and conflict incentives, we analyze the optimality of the use of conflict in the case of a mobile and renewable natural resource. The analysis allows to disentangle the effects of the various fundamentals on the emergence and timing of conflict. Specifically, it is shown that whether conflict emerges or not depends mainly on the interplay between biological/spatial characteristics of the resource (dispersal and self-retention) and economic parameters (prices). By contrast, the timing of conflict (now or later) depends mainly on initial conditions (relative scarcity due to differences in initial stock levels). The effects of certain parameters (resource growth) are shown to depend on specific trade-offs that are highlighted.

• 
  09h50 - 10h15

  Coordination problems and efficiency in an eco-epidemiological model

  • César Martinez, prés., INRA, CEE-M
  • Pierre Courtois, INRA, CEE-M
  • Mabel Tidball, INRAE
  • Gaël Thébaud, INRA, BGPI

  We consider a discrete time, finite horizon, eco-epidemiological model for the management of an outbreak impacting fruit trees. The model is designed at the landscape scale, with contamination both within and between patches, according to a linear diffusion model. No treatment is available, and management consists in detecting and removing infected trees. Agents have to decide whether they are willing to perform detection at a given cost. Within this framework, we evaluate the trade-off between keeping infected trees with less valuable production and removing them in order to avoid new infections. We compare the decentralized solution in which each agent maximizes his own utility function, with the central planner solution which maximizes the global production.
  
  Within this general framework, we analyze a two-periods-two-patches model. Using a feedback information structure, we show the existence of Nash equilibria. Exploration of the initial condition space shows that there is often a single equilibrium. However for some particular parameters and initial conditions we find multiple Nash equilibria, meaning that we are in presence of coordination problems. Mixing theoretical results and numerical simulations, we build a mapping between initial conditions (infected trees for each patch) and equilibria. Those results are compared to the central planner solution and we characterize situations in which private management leads to inefficiency.

  This work has been inspired by the management of the Sharka outbreak in France. Sharka is a viral disease responsible for important damages on fruit trees from the Prunus genus. A possible extension of our work would be to build a case study using our theoretical model together with parameters and data corresponding to this particular outbreak.

• 
  10h15 - 10h40

  Time Evolution of a Differentiated Oligopoly: The Case of Sustainable Wine

  • Michèle Breton, prés., GERAD, HEC Montréal
  • Lucia Sbragia, Durham University

  We study the time evolution of a vertically and horizontally differentiated oligopolistic industry, where firms compete in quantity and are divided into groups producing one variety of a substitutable product. We assume that firms can periodically revise their decision about which variety to produce. For a general oligopoly with two varieties, we characterize the industry composition in the steady state as a function of the parameter values. Our results are applied to the case of the sustainable wine industry, where we investigate the role of an ecolabel price premium.