Agnes Tomini

Chercheur ,  CNRS

Économie publique
Tomini
Statut
Directeur de recherche
Domaine(s) de recherche
Économie de l'environnement, Économie publique
Thèse
2009, Aix-Marseille Université
Téléchargement
CV
Contact
agnes.tomini[at]univ-amu.fr
+33(0)4 13 55 25 78
Adresse

AMU - AMSE
5-9 Boulevard Maurice Bourdet, CS 50498
​13205 Marseille Cedex 1

Résumé We formulate a hydro-economic model of the North-Western Sahara Aquifer System (NWSAS) to assess the effects of intensive pumping on the groundwater stock and examine the subsequent consequences of aquifer depletion. This large system comprises multi-layer reservoirs with vertical exchanges, all exploited under open access properties. We first develop a theoretical model to account for relevant features of the NWSAS by introducing, in the standard Gisser-Sanchez model, a non-stationary demand and quadratic stock-dependent cost functions. In the second step, we calibrate parameters values using data from the NWSAS over 1955–2000. We finally simulate the time evolution of the aquifer system with exploitation under an open-access regime. We specifically examine time trajectories of the piezometric levels in the two reservoirs, the natural outlets, and the modification of water balances. We find that natural outlets of the two reservoirs might be totally dried before 2050.
Mots clés Hydro-economic model, Private pumping, Multi aquifer system, Groundwater-dependant ecosystems, Semi-arid region, Simulation
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Résumé We analyze theoretically an institution called a “limited-tenure concession” for its ability to induce efficient public goods contribution and common-pool resource extraction. The basic idea is that by limiting the tenure over which an agent can enjoy the public good, but offering the possibility of renewal contingent on ample private provision of that good, efficient provision may be induced. We first show in a simple repeated game setting that limited-tenure concessions can incentivize socially-efficient provision of public goods. We then analyze the ability of this instrument to incentivize the first best provision for common-pool natural resources such as fish and water, thus accounting for spatial connectivity and growth dynamics of the resource. The duration of tenure and the dispersal of the resource play pivotal roles in whether this limitedtenure concession induces the socially optimal private provision. Finally, in a setting with costly monitoring, we discuss the features of a concession contract that ensure first-best behavior, but at least cost to the implementing agency.
Mots clés Concessions, Public goods, Cooperation, Natural resources, Spatial externalities, Dynamic games
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Résumé This study examines a specific class of common-pool resources whereby rivalry is not characterized by competition for the resource stock. Artesian aquifers are a typical example of such resources since the stock never depletes, even when part of the resource is extracted. We first propose a dynamic model to account for the relevant features of such aquifers such as the water pressure and well yield and characterize the corresponding dynamics. We then compare the social optimum with the private exploitation of an open-access aquifer. The comparison of these two equilibria highlights the existence of a new source of inefficiency. In the long run, this so-called pressure externality results in an additional number of wells for the same water consumption, thereby raising costs. Finally, we characterize a specific stock-dependent tax to neutralize the pressure externality.
Mots clés Dynamic optimization, Public regulation, Optimal management, Externality, Common-pool resource
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Résumé This paper proposes and analyzes the consequences of a widely-used, but little-studied institution, limited-tenure concessions, for governing club goods and common-pool resources. We first show in a simple repeated game setting that such a system can incentivize socially-efficient provision of club goods. We then extend the model to account for spatially-connected resources, an arbitrary number of heterogeneous agents, and natural resource dynamics, and show that the basic ability of limited-tenure concessions to incentivize the first best private provision is preserved in this rich setting that is more representative of natural resources such as fish, water, and game. The duration of tenure and the dispersal of the resource then play pivotal roles in whether this limited-duration concession achieves the socially optimal outcome. Finally, in a setting with costly monitoring, we discuss the features of a concession contract that ensure first-best behavior, but at least cost to the implementing agency.
Mots clés Dynamic games, Spatial externalities, Natural resources, Cooperation, Club goods, Concessions
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Résumé We compare how the long-run distribution of fishing activities is affected in multispecies fisheries when facing different second-best control rules: (1) species-specific landing regulation, and (2) global input regulation. We show how this depends on the economic returns and on the type of ecological interaction considered. We highlight specifically that fishing effort does not necessarily increase on nontargeted species and decrease on targeted species, and that the characterization of second-best efficient instruments may differ drastically depending on the nature of the interaction.
Mots clés Multispecies fisheries, Second-best management, Bioeconomic models, Fishing, Effort distribution, Biological interactions, Pêcherie, Bioéconomie
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Résumé We consider groundwater managed by a sole owner and where a perfect substitute, rainwater harvesting, is physically connected with the primary water source. This generates a marginal opportunity cost of using rainwater, since harvested water does not infiltrate. We first discuss the conditions that lead to a switch toward rainwater harvesting, then look at long-term rainwater harvesting systems. Due to limited storage capacity, long-term use of rainwater is only possible in conjunction with groundwater. We show that this only arises if the price of water is higher than the full marginal cost of rainwater harvesting. We also provide comparative statics related to this configuration, especially concerning the long-term water table. These results are finally illustrated by numerical examples. (C) 2017 Elsevier B.V. All rights reserved.
Mots clés Conjunctive use, Optimal control, Rainwater harvesting, Groundwater management
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Résumé We consider analytically the non-cooperative behavior of many private property owners who each controls the stock of a public bad such as an invasive weed species, infectious disease, fire, or agricultural pest. The stock of the public bad can grow and disperse across a spatial domain of arbitrary size. In this setting, we characterize the conditions under which private property owners will control or eradicate, and determine how this decision depends on property-specific environmental features and on the behavior of other landowners. We show that high mobility or lower control by others result in lower private control. But when the marginal dynamic cost of the bad is sufficiently large, we find that complete eradication may be privately optimal (despite the lack of consideration of others’ welfare) – in these cases, eradication arises in the non-cooperative game and is also socially optimal so there is, in effect, no externality. Finally, when property harboring the bad is not owned, or is owned in common, we derive the side payments required to efficiently control the mobile public bad.
Mots clés Externality, Externalité, Éradication, Espèce invasive
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Résumé We consider analytically the non-cooperative behavior of many private property owners who each controls the stock of a public bad such as an invasive weed species, infectious disease, fire, or agricultural pest. The stock of the public bad can grow and disperse across a spatial domain of arbitrary size. In this setting, we characterize the conditions under which private property owners will control or eradicate, and determine how this decision depends on property-specific environmental features and on the behavior of other landowners. We show that high mobility or lower control by others result in lower private control. But when the marginal dynamic cost of the bad is sufficiently large, we find that complete eradication may be privately optimal (despite the lack of consideration of others’ welfare) – in these cases, eradication arises in the non-cooperative game and is also socially optimal so there is, in effect, no externality. Finally, when property harboring the bad is not owned, or is owned in common, we derive the side payments required to efficiently control the mobile public bad
Mots clés Externality, Éradication, Externalité, Espèce invasive
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Résumé This paper studies groundwater management in the presence of rainwater harvesting (RWH). We propose a two-state model that takes into account the dynamics of the aquifer and the standard dynamics of the storage capacity, and we assume that the collection of rainwater reduces the natural recharge. We analyze the trade-off between these two water harvesting techniques in an optimal control model. In particular, we show that, when these techniques are perfect substitutes, the development of RWH leads in the long run to a depletion of the water table, even if pumping is reduced. This result is illustrated by a numerical application for the Pecos River Basin (New Mexico, USA). JEL: Q25, C61, D61. / KEY WORDS: Rainwater Harvesting, Conjunctive Use, Groundwater Management, Optimal Control.
Mots clés Economie quantitative
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Résumé In this paper, we focus on resource conservation in a model of decentralized management of groundwater and rainwater. We show that a conservation policy may have opposite effects on the level of the resource, depending on the outcome of the decentralized management. More precisely, we consider identical farmers who can use two water resources (groundwater and/or rainwater) and we study the symmetric and asymmetric feedback stationary Nash equilibria of the dynamic game. We show that a subsidy on the use of rainwater may increase the level of the aquifer at the symmetric equilibrium, whereas it decreases the level of the aquifer at the asymmetric equilibrium. This suggests that the usual focus on (interior) symmetric equilibria in dynamic games may provide misleading policy implications.
Mots clés Rainwater, Asymmetric equilibrium, Differential game, Groundwater
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Résumé This paper focuses on feedback mechanisms of remittances on the size of the migrant population. We argue that low remittances contribute to relax recipients’ credit constraints and foster further emigration. On the other hand, high remittances may deter migration if they make further emigration unnecessary. Thus, remittances can be considered as a contaminating factor in an epidemic model of migration. This model allows us to characterize a rich set of situations in order to appraise the impact of different policies on the total number of migrants. For instance, we show the mechanisms through which a policy aiming at making migrants successful in the host country may finally lower migration.
Mots clés Dynamic Analysis, Epidemic Modeling, Remittances, Migration
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Résumé We examine the efficiency, distributional, and environmental consequences of assigning spatial property rights to part of a spatially-connected natural resource while the remainder is competed for by an open access fringe. We refer to this as partial enclosure of the commons. We obtain sharp analytical results regarding partial enclosure of the commons including: (1) While second best, it typically improves welfare relative to no property rights, (2) all resource users can be made better off, (3) positive rents arise in the open access area, and (4) the resource maintains higher stocks. Under spatial heterogeneity, we also characterize spatial regions that are ideal candidates for partial enclosure - typically, society should seek to enclose those patches with high environmental productivity and high self-retention, but whether high economic productivity promotes or relegates a patch may depend on one’s objective.
Mots clés Incomplete property rights, Common property, Natural resources
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Résumé This paper discusses the framing of the model of Gisser and Sánchez (1980) [9] which is commonly reproduced by the follow-up literature. We note that results on the magnitude of welfare gains from optimal groundwater management are affected by the models׳ limitations, such as the commonly used assumption on the linear relationship between pumping cost and the water table level, and the absence of considerations for non-consumptive benefits. We question the appropriateness of these assumptions since the stock effect (the dependence of extraction cost and/or that of benefits on the stock of resource) affects the time variation of the shadow price. We demonstrate that this leads to a declining value of in situ resource over time. As such, its addition on marginal extraction cost may be negligible, and consequently favors the validation of the Gisser-Sánchez effect.
Mots clés Rent, Scarcity
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Résumé This paper is concerned with discrete choice contingent value estimate when the respondents are uncertain about the environmental amenities. Within a class of indirect utility functions often used in empirical studies, we put forwards the effect of the risk premium on the WTP. We then show how this risk premium also modifies the estimation procedure. A Monte Carlo experiment concludes the paper by putting forward a mis-estimation of the WTP when this uncertainty is ignored, more precisely when we focus on the effect of the risk premium.
Mots clés Risk premium, Parametric models, Contingent valuation
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Résumé This paper extends the standard two-period prevention model by incorporating anticipatory emotions. We introduce an additional cost, referred as the emotional load, which is endogenously determined by future risk but can be mitigated by current preventive effort. We show that a more intense emotional load incentivizes the emotional agent to increase investment in either self-insurance or self-protection. By contrast, greater uncertainty sensitivity has an ambiguous effect: It depends on the curvature of the emotional load function and wealth. When savings are substitutes, the effect of these parameters may diverge, whereas they align when savings are complements to risk prevention. Finally contrasting our setting with a setting without uncertainty or emotions, we show that, under prudence, the introduction of a zero-mean risk leads to a higher optimal level of self-insurance. Anxiety amplifies the incentive to reduce risk by lowering present well-being.
Mots clés Uncertainty, Anticipatory emotions, Self-protection, Self-insurance
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Résumé We examine the efficiency and environmental consequences of assigning species-specific common-property rights, considering a Lotka-Volterra model in which fisheries are specialized in the harvesting of a single species. We show that the fragmentation of the ecosystem implies the tragedy of the anticommons even when fisheries compete for the resource. Indeed, contrasting the private exploitation equilibrium with the socially optimal solution, we demonstrate that the predator stock is too high while the prey stock is too low under private property rights. A puzzling result is that the "abundant" species is actually underused because of insufficient economic incentives; however, the scarce and high-priced species does not necessarily suffer from overexploitation. Biological interactions are consequently the main driver of stock depletion. Finally, we investigate how to simultaneously solve both the tragedy of the commons and that of the anticommons and analyze the economic costs of regulating only the tragedy of the commons.
Mots clés Exclusive property rights Common-pool resource Anticommons Fisheries, Exclusive property rights, Optimal control, Prey-predator relationship, Fisheries, Anticommons, Common-pool resource
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Résumé We formulate a hydro-economic model of the NorthWestern Sahara Aquifer System (NWSAS) to assess the effects of intensive pumping on the groundwater stock and examine the subsequent consequences of aquifer depletion. This large system comprises multi-layer reservoirs with vertical exchanges, all exploited under open access properties. We first develop a theoretical model to account for relevant features of the NWSAS by introducing, in the standard Gisser-Sanchez model, a non-stationary demand and quadratic stock-dependent cost functions. In the second step, we calibrate parameters values using data from the NWSAS over 1955-2000. We finally simulate the time evolution of the aquifer system with exploitation under an open-access regime. We specifically examine time trajectories of the piezometric levels in the two reservoirs, the natural outlets, and the modification of water balances. We find that natural outlets of the two reservoirs might be totally dried before 2050.
Mots clés Groundwater-dependant ecosystems, Semi-arid region, Simulation, Multi aquifer system, Private pumping, Hydro-economic model
Télécharger HAL Google Scholar
Résumé This paper studies a specific class of common-pool resources whereby rivalry is not characterized by competition for the resource stock. Artesian aquifers have been identified as a typical example, since the stock is never depleted, even when part of the resource is extracted. We first propose a dynamic model to account for relevant features of such aquifers-like water pressure, or well yield-and to characterize the corresponding dynamics. We then compare the social optimum and the private exploitation of an open-access aquifer. The comparison of these two equilibria allows us to highlight the existence of a new source of inefficiency. We refer to this as pressure externality. This externality results in the long run in an additional number of wells for the same water consumption, and hence additional costs. Finally, we characterize a specific stock-depend tax to neutralize the pressure externality. JEL Classification: H21, H23, Q15, Q25, C61
Mots clés Dynamic optimization, Public regulation, Optimal management, Externality, Common-pool resource
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Résumé Rainwater harvesting, consisting in collecting runoff from precipitation, has been widely developed to stop groundwater declines and even raise water tables. However this expected environmental effect is not self-evident. We show in a simple setting that the success of this conjunctive use depends on whether the runoff rate is above a threshold value. Moreover, the bigger the storage capacity, the higher the runoff rate must be to obtain an environmentally efficient system. We also extend the model to include other hydrological parameters and ecological damages, which respectively increase and decrease the environmental efficiency of rainwater harvesting.
Mots clés Groundwater management, Rainwater harvesting, Optimal control, Conjunctive use
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