Coherent Cost-Sharing Rules

We reconsider the discrete version of the axiomatic cost-sharing model. We propose a condition of (informational) coherence requiring that not all informational refinements of a given problem be solved differently from the original problem. We prove that strictly coherent linear cost-sharing rules must be simple random-order rules.

Responsibility and Cross-Subsidization in Cost Sharing

We propose two axiomatic theories of cost sharing with the common premise that agents demand comparable -though perhaps different- commodities and are responsible for their own demand. Under partial responsibility the agents are not responsible for the asymmetries of the cost function: two agents consuming the same amount of output always pay the same price; this holds true under full responsibility only if the cost function is symmetric in all individual demands. If the cost function is additively separable, each agent pays her stand alone cost under full responsibility; this holds true under partial responsibility only if, in addition, the cost function is symmetric. By generalizing Moulin and Shenker’s (1999) Distributivity axiom to cost-sharing methods for heterogeneous goods, we identify in each of our two theories a different serial method. The subsidy-free serial method (Moulin, 1995) is essentially the only distributive method meeting Ranking and Dummy. The cross-subsidizing serial method (Sprumont, 1998) is the only distributive method satisfying Separability and Strong Ranking. Finally, we propose an alternative characterization of the latter method based on a strengthening of Distributivity.

Ordinal Cost Sharing.

We ask how the three known mechanisms for solving cost sharing problems with homogeneous cost functions - the value, the proportional, and the serial mechanisms - should be extended to arbitrary problem. We propose the Ordinality axiom, which requires that cost shares be invariante under all transactions preserving the nature of a cost sharing problem.

An Axiomatization of the Serial Cost-Sharing Method

We o¤er an axiomatization of the serial cost-sharing method of Friedman and Moulin (1999). The key property in our axiom system is Group Demand Monotonicity, asking that when a group of agents raise their demands, not all of them should pay less.

Sharing the Cost of a Public Good: an Incentive-Constrained Axiomatic Approach

We study the problem of provision and cost-sharing of a public good in large economies where exclusion, complete or partial, is possible. We search for incentive-constrained efficient allocation rules that display fairness properties. Population monotonicity says that an increase in population should not be detrimental to anyone. Demand monotonicity states that an increase in the demand for the public good (in the sense of a first-order stochastic dominance shift in the distribution of preferences) should not be detrimental to any agent whose preferences remain unchanged. Under suitable domain restrictions, there exists a unique incentive-constrained efficient and demand-monotonic allocation rule: the so-called serial rule. In the binary public good case, the serial rule is also the only incentive-constrained efficient and population-monotonic rule.

Nearly Serial Sharing Methods

A group of agents participate in a cooperative enterprise producing a single good. Each participant contributes a particular type of input; output is nondecreasing in these contributions. How should it be shared? We analyze the implications of the axiom of Group Monotonicity: if a group of agents simultaneously decrease their input contributions, not all of them should receive a higher share of output. We show that in combination with other more familiar axioms, this condition pins down a very small class of methods, which we dub nearly serial.

Aumann-Shapley Pricing : A Reconsideration of the Discrete Case

We reconsider the following cost-sharing problem: agent i = 1,...,n demands a quantity xi of good i; the corresponding total cost C(x1,...,xn) must be shared among the n agents. The Aumann-Shapley prices (p1,...,pn) are given by the Shapley value of the game where each unit of each good is regarded as a distinct player. The Aumann-Shapley cost-sharing method assigns the cost share pixi to agent i. When goods come in indivisible units, we show that this method is characterized by the two standard axioms of Additivity and Dummy, and the property of No Merging or Splitting: agents never find it profitable to split or merge their demands.

Fair Allocation of Production Externalities: Recent Results

We survey recent axiomatic results in the theory of cost-sharing. In this litterature, a method computes the individual cost shares assigned to the users of a facility for any profile of demands and any monotonic cost function. We discuss two theories taking radically different views of the asymmetries of the cost function. In the full responsibility theory, each agent is accountable for the part of the costs that can be unambiguously separated and attributed to her own demand. In the partial responsibility theory, the asymmetries of the cost function have no bearing on individual cost shares, only the differences in demand levels matter. We describe several invariance and monotonicity properties that reflect both normative and strategic concerns. We uncover a number of logical trade-offs between our axioms, and derive axiomatic characterizations of a handful of intuitive methods: in the full responsibility approach, the Shapley-Shubik, Aumann-Shapley, and subsidyfree serial methods, and in the partial responsibility approach, the cross-subsidizing serial method and the family of quasi-proportional methods.

Equal Factor Equivalence in Economies with Multiple Public Goods.

We consider the problem of provisioon and cost-sharing of multiple public goods. the efficient equal factor equivalent allocation rule makes every agent indifferent between what he receives and the opportunity of choosing the bundle of public goods subject to the constraint of paying r times its cost, where r is set as low as possible.

Production externalities : cooperative and non-cooperative approaches

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Essais en microéconomie théorique et appliquée

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La prise en compte de l’adaptation au changement climatique dans les politiques publiques de verdissement (2005-2015) : le cas de Montréal

Les connaissances scientifiques sur le changement climatique (CC) évoluent rapidement. Toutefois, des incertitudes persistent sur l’étendue de ses conséquences, particulièrement dans les milieux urbains, qui subiront des impacts différents de ceux vécus par les milieux ruraux. Les autorités publiques ont récemment commencé à élaborer des politiques publiques d’adaptation au changement climatique (ACC) qui visent à en limiter les conséquences indésirables. En milieu urbain, la littérature suggère qu’un des outils que devraient privilégier ces politiques est le verdissement. Des auteurs signalent que les actions visant l’ACC peuvent se greffer dans des politiques existantes. L’ACC, comme enjeu public, peut donc être réalisée par l’entremise de sa prise en compte dans les politiques publiques de verdissement. Cette prise en compte devrait affecter le contenu (quoi?) et le pilotage (comment?) des différentes étapes des politiques. Le cas de la politique publique de verdissement de la Ville de Montréal, au Québec, nous a permis d’étudier cette prise en compte. En utilisant un cadre d’analyse des politiques publiques développé par Knoepfel et al. (2015), qui porte entre autres sur la mobilisation des ressources par différents acteurs concernés par ces politiques, nous montrons que cette dernière s’est opérée de quelques façons. Premièrement, il y a eu un changement dans l’argumentaire pour le verdissement, outil qui vise à lutter contre les îlots de chaleur urbains et assurer une meilleure gestion des eaux pluviales. Ensuite, le choix de l’échelle d’agglomération pour la prise en compte de l’ACC a entraîné un changement d’échelle dans la gestion du verdissement. La publication d’un plan d’action majeur de verdissement urbain pour l’agglomération, et dont le leitmotiv est l’ACC, le démontre. Quelques modifications réglementaires et l’inclusion de nouveaux acteurs dans la politique témoignent aussi que la prise en compte a eu lieu. Finalement, le plan d’action fournit un cadre pour la mise en œuvre du verdissement dans les zones les plus vulnérables au CC en plus d’une structure de partage des coûts. Cependant, la mise en oeuvre du verdissement dans une visée d’ACC n'a pas été évaluée dans la présente étude. Nous avons aussi noté que la biodiversité est un enjeu d’importance qui va de pair avec l’ACC dans la politique de verdissement. Il y a donc une prise en compte, partielle, de l’ACC dans la politique publique de verdissement à Montréal (avec certains écueils). Nous arguons que l’enjeu de l’ACC sert peut-être d’argument supplémentaire pour verdir la ville plutôt que d’être un véritable moteur de transformation de la politique de verdissement.

Sharing the Cost of a Public Good without Subsidies

We study the construction of a social ordering function for the case of a public good financed by contributions from the population, and we extend the analysis of Maniquet and Sprumont (2004) to the case when contributions cannot be negative, i.e. agents cannot receive subsidies from others.

Information Sharing and the Stability of Cooperation in Research Joint Ventures.

The model studies information sharing and the stability of cooperation in cost reducing Research Joint Ventures (RJVs). In a four-stage game-theoretic framework, firms decide on participation in a RJV, information sharing, R&D expenditures, and output. An important feature of the model is that voluntary information sharing between cooperating firms increases information leakage from the RJV to outsiders. It is found that it is the spillover from the RJV to outsiders which determines the decision of insiders whether to share information, while it is the spillover affecting all firms which determines the level of information sharing within the RJV. RJVs representing a larger portion of firms in the industry are more likely to share information. It is also found that when sharing information is costless, firms never choose intermediate levels of information sharing : they share all the information or none at all. The size of the RJV is found to depend on three effects : a coordination effect, an information sharing effect, and a competition effect. Depending on the relative magnitudes of these effects, the size of the RJV may increase or decrease with spillovers. The effect of information sharing on the profitability of firms as well as on welfare is studied.