CES Economic Theory Seminar

Add Headings and they will appear in your table of contents.

Friday, May 21 st, 2021 : William Zwicker (Union College)

https://zoom.univ-paris1.fr/j/92167705411?pwd=dDVOT1lyZmZ1N0ZlV2FzSk5KNTZSZz09

pwd: 369238

meeting number: 921 6770 5411

Title : Fair division of graphs and of tangled cakes

Summary: Fair Division is studied in both the continuous context (a single divisible “cake” is modeled by the [0, 1] interval) and the discrete (a pile of indivisible objects will be divided into sub-piles). One strand of the continuous literature seeks to award a single connected piece (a subinterval) as each agent’s share; what is the analogue for the discrete case? In fair division of a graph, the indivisible graph vertices are allocated to the agents, with each share of vertices required to induce a connected subgraph. When the envy freeness fairness criterion is adjusted to handle indivisible objects and applied to graphs, however, positive results for three or more agents have been limited – until recently – to Hamiltonian graphs (graphs with a path visiting each vertex exactly once). QUESTION: Is this limitation fundamental?

We introduce tangles – a new context for fair division. A tangle is a connected topological space constructed by gluing together several copies of the unit interval [0, 1]. We explore which tangles guarantee envy-free allocations of connected shares for n agents. Each single tangle T corresponds in a natural way to an infinite topological class G(T) of graphs. This correspondence links fair division of tangles to EFk_outer fair division of graphs, in a way that yields partial answers to our question. Loosely speaking, the answers are “No, if three agents are sharing the graph,” but “Yes, if arbitrarily many agents".

Friday, May 7th, 2021 : Olivier Gossner (Ecole Polytechnique)

https://zoom.univ-paris1.fr/j/92167705411?pwd=dDVOT1lyZmZ1N0ZlV2FzSk5KNTZSZz09

pwd: 369238

meeting number: 921 6770 5411

Title : Strategic type space

Summary: Given any finite game with incomplete information we define strategic type spaces (STS) as representations of players’ strategically relevant information for interim correlated rationalizable play. We construct the set of all hierarchies of best-replies and show that they form a universal STS that is minimal among all STS. We then study the representation of incomplete information perturbations on the minimal STS. Finally, we characterize robustness to incomplete information in terms of a dynamic optimization problem over a finite state space.

Friday, April 16th, 2021 : Bernhard von Stengel (LSE)

https://zoom.univ-paris1.fr/j/92167705411?pwd=dDVOT1lyZmZ1N0ZlV2FzSk5KNTZSZz09

pwd: 369238

meeting number: 921 6770 5411

Title : Algorithms for Rank-1 Bimatrix Games

Summary: The rank of a bimatrix game is the matrix rank of the sum of the two payoff matrices. For a game of rank r, the set of its Nash equilibria is the intersection of a one-dimensional set of equilibria of parameterized games of rank r-1 with a hyperplane. We comprehensively analyze games of rank one. They are economically more interesting than zero-sum games (which have rank zero), but are nearly as easy to solve. We show the following results: (1) One equilibrium of a rank-1 game can be found in polynomial time by binary search. (2) All equilibria of a rank-1 game can be found by a pivoting method that follows a piecewise linear path. In contrast, such a path-following method finds only one equilibrium of a general bimatrix game. (3) The number of equilibria of a rank-1 game may be exponential. (4) We present a new rank-preserving homeomorphism between bimatrix games and their equilibrium correspondence. It is a variation of the Kohlberg-Mertens homeomorphism used for the concept of strategic stability of an equilibrium component.

Joint work with Bharat Adsul, Jugal Garg, Ruta Mehta, and Milind Sohoni.

Published 2021 in Operations Research 69(2), 613-631.

Friday, April. 9th, 2021 : Igal Milchtaich (Bar Ilan University)

https://zoom.univ-paris1.fr/j/92167705411?pwd=dDVOT1lyZmZ1N0ZlV2FzSk5KNTZSZz09

pwd: 369238

meeting number: 921 6770 5411

Title : Agnostic sequential rationality

Summary: Agnostic sequential equilibrium is a refinement of sequential equilibrium that does not force on theplayers asingle, arbitrarybeliefsystem. In fact, a strategy profile in an imperfect-information extensive-form game with perfect recall is an ASE if and only if it isasequential equilibrium with every fully consistent belief system. However, ASE is not defined in terms of full consistency (which employsperturbations of strategies) but is based on a simpler, localconcept of strong consistencybetween strategy profiles and off-equilibrium beliefs, which is applicable to a large class of dynamic games, including gameswith a continuum of actions. In this, the new solution concept is similar to perfect Bayesian equilibrium. ASE is generalized by the set-valued solution concept of agnostic sequential polyequilibrium, which allows leaving the players’ actions in some(or all)information setspartially or completely unspecified.

Link to full paper: https://faculty.biu.ac.il/~milchti/papers/sequential.pdf

Friday, April 2nd, 2021 : Mattias Nunez (Ecole Polytechnique)

https://zoom.univ-paris1.fr/j/92167705411?pwd=dDVOT1lyZmZ1N0ZlV2FzSk5KNTZSZz09

pwd: 369238

meeting number: 921 6770 5411

Title : Voting by Simultaneous Vetoes

Summary: We design a class of voting mechanisms, simultaneous veto mechanisms, that ensure that each equilibrium outcome is Pareto efficient under a very weak condition for extending preferences over lotteries. In these mechanisms, each voter submits a list of alternatives to be vetoed and the winner is selected randomly from the nonvetoed alternatives. Each equilibrium outcome guarantees each voter a minimal level of satisfaction and each Nash equilibrium is immune to credible coalitional deviations (coalition-proof). Finally, we derive the conditions necessary for a Pareto-efficient rule to be implementable through a mechanism that ensures that each equilibrium is coalition-proof.

Friday, March 26th, 2021 : Franz Dietrich (CES)

https://zoom.univ-paris1.fr/j/92167705411?pwd=dDVOT1lyZmZ1N0ZlV2FzSk5KNTZSZz09

pwd: 369238

meeting number: 921 6770 5411

Title : Dynamically Rational Judgment Aggregation

Summary: Judgment aggregation is the aggregation of yes/no judgments of different individuals on different propositions. Judgment aggregation theory has always focused on the attainment of rational collective judgments. But so far, rationality has been understood in static terms: as “coherence” of judgments at a given time, regarded as consistency, completeness, and/or deductive closure. By contrast, this paper analyses whether collective judgments can be dynamically rational, so that they change rationally in response to new information. Formally, a judgment aggregation rule is dynamically rational with respect to a given revision operator if, whenever all individuals revise their judgments in light of some information (a learnt proposition), then the new aggregate judgments are the old ones revised in light of this information, i.e., aggregation and revision commute. We prove a general impossibility theorem: if the propositions on the agenda are sufficiently interconnected, no judgment aggregation rule with standard properties is dynamically rational with respect to any revision operator satisfying some mild conditions (familiar from belief revision theory). Our theorem is a dynamic-rationality counterpart of some well-known impossibility theorems for static rationality. We also explore how dynamic rationality might be achieved by relaxing some of the conditions in the theorem, especially by using premise-based aggregation rules.

Link: http://franzdietrich.net/Papers/DietrichList-DynamicallyRationalJA.pdf

Friday, March 19th, 2021 : Felix Brandt (Technische Universität München)

https://zoom.univ-paris1.fr/j/92167705411?pwd=dDVOT1lyZmZ1N0ZlV2FzSk5KNTZSZz09

pwd: 369238

meeting number: 921 6770 5411

Title : Justifying optimal play via consistency

Summary: Developing normative foundations for optimal play in two-player zero-sum games has turned out to be surprisingly difficult, despite the powerful strategic implications of the Minimax Theorem. We characterize maximin strategies by postulating coherent behavior in varying games. The first axiom, called consequentialism, states that how probability is distributed among completely indistinguishable actions is irrelevant. The second axiom, consistency, demands that strategies that are optimal in two different games should still be optimal when there is uncertainty which of the two games will actually be played. Finally, we impose a very mild rationality assumption, which merely requires that strictly dominated actions will not be played. Our characterization shows that a rational and consistent consequentialist who ascribes the same properties to his opponent has to play maximin strategies. This result can be extended to characterize Nash equilibrium in bimatrix games whenever the set of equilibria is interchangeable.

Friday, March 12th, 2021 : Xiangyu Qu (CES)

https://zoom.univ-paris1.fr/j/92167705411?pwd=dDVOT1lyZmZ1N0ZlV2FzSk5KNTZSZz09

pwd: 369238

meeting number: 921 6770 5411

Title : On the Robust Measurement of Inequality

Summary: In practice, a dataset used for calculating inequality index does not always present in a single statistic fashion. A robust inequality measure, in the face of a multi-valued statistic dataset, is needed and should take into account both inequality and imprecision concerns in a proper way. However, we find that a commonly used approach is problematic in imprecision reduction. We therefore suggest a new approach of robust inequality measure which surmounts the difficulty. This approach naturally generalizes the Atkinson and Gini indices to measure multi- valued problems. We finally axiomatize two social welfare functions which induce the robust Atkinson and the robust Gini indices.

Friday, March 5th, 2021 : Kostas Bimpikis (Stanford University)

PLEASE NOTE: Exceptionally the seminar will take place at 4pm

https://zoom.univ-paris1.fr/j/92619722047?pwd=MzlTdlErcVo0UDFSS2M2V0FxNmdkQT09

ID de réunion : 926 1972 2047

Code secret : 352983

Title : Data Tracking under Competition

Summary: We explore the welfare implications of data tracking technologies that enable firms to collect consumer data and potentially use it for price discrimination. The model we develop centers around two features: first, competition between firms and, second, consumers' level of sophistication. Our baseline environment features a firm that can collect information about the consumers it transacts with in a duopoly market, which it can then use in a second monopoly market. We characterize and compare the equilibrium outcomes in three settings of interest: (i) an economy with myopic consumers, who, when making purchase decisions, do not internalize the fact that firms have the ability to track their behavior and use this information in future transactions, (ii) an economy with \textit{forward-looking} consumers, who take into account the implications of data tracking when determining their actions, and (iii) an economy where no data tracking technologies are used either due to technological or regulatory constraints. We find that the absence of data tracking may lead to a decrease in consumer surplus, even when consumers are myopic. Importantly, this result relies critically on competition: consumer surplus is higher when data tracking technologies are used in the marketplace only when multiple firms offer substitutable products to consumers. Our results contribute to the debate of whether to regulate firms’ use of data tracking technologies by illustrating that their effect on consumers depends not only on their level of sophistication, i.e., the extent to which they internalize how their data may be used, but also on the degree of competition in the market. Finally, in contrast to earlier work, we show that firms may have no incentive to self-regulate their use of consumer data even when consumers fully internalize and anticipate how their data may be used.

Fridays, February 19th and 26th, 2021 : Spring break, no seminar

Friday, February 12th, 2021 : Stefano Moretti (Lamsade, Paris Dauphine)

https://zoom.univ-paris1.fr/j/92619722047?pwd=MzlTdlErcVo0UDFSS2M2V0FxNmdkQT09

ID de réunion : 926 1972 2047

Code secret : 352983

Title : Social ranking solutions for coalitional situations

Summary: In the literature of cooperative games, the notion of power index has been widely used to evaluate the “influence'” of individual players (e.g., voters, political parties, nations, stockholders, etc.) involved in a collective decision process, i.e., their ability to force a decision in situations like an electoral system, parliament, governing council, management board, etc. In practical situations, however, the information concerning the strength of coalitions and their effective possibilities of cooperation is not easily accessible due to heterogeneous and hardly quantifiable factors about the performance of groups, their bargaining abilities, the power obtained by threatening not to cooperate with other players, etc. So, any attempt to numerically represent the influence of groups and individuals conflicts with the complex and multi-attribute qualitative nature of the problem. For these reasons, we introduced new solutions to provide a more flexible theory of cooperative interaction situations and power indices based on the evidence that the nature of available information about the interaction of individuals and groups is mostly ordinal. The goal of this talk is therefore to provide a general introduction to basic notions and some recent results related to social ranking solutions and their properties.

References

Allouche, T., Escoffier, B., Moretti, S. and Öztürk, M., 2020, July. Social Ranking Manipulability for the CP-Majority, Banzhaf and Lexicographic Excellence Solutions. In 29th International Joint Conference on Artificial Intelligence and 27th Pacific Rim International Conference on Artificial Intelligence(IJCAI-PRICAI-20), pp. 17-23.

Bernardi, G., Lucchetti, R. and Moretti, S., 2019. Ranking objects from a preference relation over their subsets. Social Choice and Welfare, 52(4), pp.589-606.

Haret, A., Khani, H., Moretti, S. and M Öztürk, M., 2018, July. Ceteris paribus majority for social ranking. In 27th International Joint Conference on Artificial Intelligence (IJCAI-ECAI-18), pp. 303-309.

Khani, H., Moretti, S. and Öztürk, M., 2019. An ordinal Banzhaf index for social ranking. In 28th International Joint Conference on Artificial Intelligence(IJCAI 2019), pp. 378-384.

Friday, February 5th, 2021 : Philippe Jéhiel (PSE)

https://zoom.univ-paris1.fr/j/92619722047?pwd=MzlTdlErcVo0UDFSS2M2V0FxNmdkQT09

ID de réunion : 926 1972 2047

Code secret : 352983

Title : Analogy-based expectation equilibrium and related concepts: Theory, applications, and beyond

Summary: In this survey, I provide a unified definition of analogy-based expectation equilibrium (ABEE) for strategic environments involving multiple stages and private information. I discuss various alternative interpretations of the concept as well as how to use ABEE in practice. I review a variety of applications including two new ones related to speculative trading and personnel economics. I then discuss a number of alternative equilibrium concepts emphasizing the links and didderences with ABEE. Finally, I discuss possible next steps in particular related to the endogeneization of analogy partitions.

Friday, January 29th, 2021 : Van Quy Nguyen (CES)

https://zoom.univ-paris1.fr/j/92619722047?pwd=MzlTdlErcVo0UDFSS2M2V0FxNmdkQT09

ID de réunion : 926 1972 2047

Code secret : 352983

Title : Endowment-regarding preferences

Summary: We consider a general equilibrium model of pure exchange economies with endowment externalities. Consumers’ behaviors depend not only on their own consumption but also on the endowments of the other consumers. Applying the same method of analysis in Balasko (2015) about wealth concerns, we first show that almost all properties of equilibrium, including smooth equilibrium manifold and genericity of regular economies, can be directly extended to the economy where the demand function depends on the endowments of others and wealth of only one consumer. Next, we clarify the sufficient conditions under which those properties remain true in the economy with the most general form of endowment externalities. Finally, we generalize the above sufficient conditions to derive generic regularity results in the economy with both consumption and endowment externalities.

Friday, January 22nd, 2021 : Fedor Sandomirskiy (Technion / HSE St.Petersburg)

https://zoom.univ-paris1.fr/j/92619722047?pwd=MzlTdlErcVo0UDFSS2M2V0FxNmdkQT09

ID de réunion : 926 1972 2047

Code secret : 352983

Title : Feasible joint posterior beliefs

Summary: We study the set of possible joint posterior belief distributions of a group of agents who share a common prior regarding a binary state, and who observe some information structure. For two agents we introduce a quantitative version of Aumann's Agreement Theorem and show that it is equivalent to a characterization of feasible distributions due to Dawid et al. (1995). For any number of agents, we characterize feasible distributions in terms of a "no-trade" condition. We use these characterizations to study information structures with independent posteriors. We also study persuasion problems with multiple receivers, exploring the extreme feasible distributions.

Friday, January 15th, 2021 : Andy Zapechelnyuk (University of Saint Andrews)

https://zoom.univ-paris1.fr/j/92619722047?pwd=MzlTdlErcVo0UDFSS2M2V0FxNmdkQT09

ID de réunion : 926 1972 2047

Code secret : 352983

Title : Compromise, don't optimize : Generalizing perfect Bayesian equilibrium to games with ambiguity

Summary: We introduce a solution concept for extensive-form games of incomplete information in which players need not assign likelihoods to what they do not know. This is embedded in a model in which players can hold a set of beliefs. Players make choices by looking for compromises that yield a good performance under each of their beliefs. Our solution concept is called perfect compromise equilibrium. It generalizes perfect Bayesian equilibrium. We show how it deals with uncertainty without using probabilities in Cournot and Bertrand markets, Spence's job market signaling, as well as in bilateral trade with common value.

Friday, January 8th, 2021 : Bhaskar Dutta (University of Warwick)

https://zoom.univ-paris1.fr/j/95098377878?pwd=Y2Y2aENPcWlHbmt4NTc5ME1WdjJvUT09

ID de réunion : 950 9837 7878

Code secret : 538974

Title : Attack and Interdiction in Networks

Summary: We model a game between an attacker A and n target nodes. Each target has a different value for the attacker. Each target node i is a distinct player, and can invest in a technology to intercept the object with some probability at a quadratic cost. The attacker is interpreted as a terrorist or criminal, whose objective is to transport an object (a bomb, biological agent, contraband goods, or a packet of drugs) from his location (labeled 0) to one of the defenders’ locations. The defenders and attacker are connected by an undirected network G which is interpreted as a transportation network (e.g. airline or road network) that can be used by the attacker to transport the object. In our baseline model, we assume that the detection technology involves a fixed cost. All players choose their strategies simultaneously, so that the appropriate solution concept is Nash equilibrium. In an extension, we assume that the detection technology involves a variable cost. In this case, the targets can decide whether to inspect a “suspicious” package when it arrives at its destination taking into account all available information. This then involves sequential decision-making and we use sequential equilibrium as a solution concept.

Our main result shows that there is a unique Nash equilibrium. We then go on to describe two kinds of comparative statics results. In one, we discuss how the equilibrium outcomes change when an additional link is added to the network. In the second type, we describe how the equilibrium outcomes change when there is a small increase in the value of a target node. It turns out that in both cases, the changes in equilibrium payoff to the attacker can be counterintuitive. In particular, an additional link should increase the payoff of the attacker since this gives the attacker more options of attack. We show that an analogue of Braes Paradox can occur in our model - the attacker’s equilibrium payoff can be strictly lower! A similar counterintuitive result can occur even in the second case - the attacker’s equilibrium payoff may be strictly lower when the value of a node increases.

We go on to study sequential equilibria in our model. We show that under relatively weak genericity assumptions, there cannot be a mixed strategy sequential equilibrium when G is a tree. We then go on to construct pure strategy sequential equilibria when the network is either a line or a star. We also construct an example to show that sequential equilibria need to be unique.

Finally, we look at an alternative formulation where a single centralised agency coordi- nates defence. We focus on the line and show that equilibrium is unique. We also identify conditions under which all nodes in the line will be attacked in equilibrium and compare the equilibrium outcomes under the cooperative and non-cooperative formulations. Not surprisingly, the attacker is worse off in the case of centralised defence.

Friday, December 11th, 2020 : Robert Gary-Bobo (CES)

https://zoom.univ-paris1.fr/j/95098377878?pwd=Y2Y2aENPcWlHbmt4NTc5ME1WdjJvUT09

ID de réunion : 950 9837 7878

Code secret : 538974

Title : Bargaining over Treatment Choice under Disagreement

Summary: A group of experts with different prior beliefs must make a collective decision over the choice of a treatment. A dataset is made public and leads to revisions of their beliefs. We propose a model where the experts’ disagreements are resolved through bargaining, and focus on the Nash bargaining solution. With the Nash bargaining solution, the collective decision is made as if a planner maximized expected utility with respect to a “compromise belief” that places greater weight on the more pessimistic experts. We view experts as typically bargaining after disclosure of the dataset: in well-behaved problems, this leads to solutions that are ex ante Pareto-inefficient. In interesting classes of problems, bargaining leads to an inefficient use of information in a stronger sense: experts receive a lower payoff in every state, and thus for any prior belief (i.e., inadmissibility). Inefficiency takes the form of under-reaction to information (i.e., inertia) as compared to the solution generated by the normative solution in which experts bargain on the procedure used to exploit the dataset, before its disclosure (i.e., ex ante bargaining). We suggest applications of this model, not only to collective decision-making, but also to problems of statistical inference, and connect our approach to Bayesian model averaging.

Friday, December 4th, 2020 : Olivier Tercieux (PSE)

https://zoom.univ-paris1.fr/j/95098377878?pwd=Y2Y2aENPcWlHbmt4NTc5ME1WdjJvUT09

ID de réunion : 950 9837 7878

Code secret : 538974

Title : Unpaid Kidney Exchange: Overcoming double coincidence of wants without money

Summary: For an incompatible patient-donor pair, kidney exchanges often forbid receipt-before-donation (the patient receives a kidney before the donor donates) and donation-before-receipt, causing a double-coincidence-of-wants problem. Our proposal, the Unpaired kidney exchange algorithm, uses “memory” as a medium of exchange to eliminate these timing constraints. In a dynamic matching model, we prove that Unpaired delivers a waiting time of patients close to optimal and substantially shorter than currently utilized state-of-the-art algorithms. Using a rich adminis- trative dataset from France, we show that Unpaired achieves a match rate of 57 percent and an average waiting time of 440 days. The (infeasible) optimal algorithm is only slightly better (58 percent and 425 days); state-of-the-art algorithms deliver less than 34 percent and more than 695 days. We draw similar conclusions from the simulations of two large U.S. platforms. Lastly, we propose a range of solutions that can address the potential practical concerns of Unpaired.

Friday, November 27th, 2020 : Nicolas Vieille (HEC)

https://zoom.univ-paris1.fr/j/95098377878?pwd=Y2Y2aENPcWlHbmt4NTc5ME1WdjJvUT09

ID de réunion : 950 9837 7878

Code secret : 538974

Title : Consensus in social learning: an overview

Summary: In this talk, we will give a selected overview of some results in social learning models. These are dynamic, incomplete information models where agents with similar preferences learn over time from observing the behavior of other agents. Some central questions are whether a consensus eventually emerges and how quicky, and whether this consensus reflects all privately available information.

Friday, November 20th, 2020 : No Economic Theory Seminar. The "Journées CES" are held on this date.

Link to the sessions of the "journées CES" :

https://zoom.univ-paris1.fr/j/99860677682?pwd=UWpDUk1vMlA4bkZnRGdSQTlRMm82QT09

ID de réunion : 998 6067 7682

Code secret : 046305

Friday November 13th, 2020 : Carmen Camacho (PSE)

https://zoom.univ-paris1.fr/j/91585767589?pwd=OElHeHhvV2wwNHNES1RSQXlJclFvZz09

Nº de réunion : 915 8576 7589

Title : Optimal profit making and the firm's environmental responsability

Abstract : The Environmental, Social, and Governance (ESG) criteria are a rising approach to responsible investment. ESG corresponds to an aggregation of standards in measuring sustainability and a consolidation of the investment decisions with social and moral impacts in the society. The ESG criteria have been visibly remodeling firms' investment and as a result, in the last decades some firms are devoted to be ethically, socially, and environmentally sustainable in the last few decades. In this wise, firms aim to possess social impact and financial gain within the market.

In this article, we study first the problem of a single chevalier firm, which optimizes overall profits over an infinite time period taking the trajectory of capital as given. The firm knows how production drives environmental quality and takes it into consideration. The firm's discount rate plays an extremely important role and it is not required to be negative. In a second moment, we study a full-fledged problem in which a representative household provides capital to the firm. We contribute to the literature on the social role of the firm by showing that if a firm cares about the environment and takes the future into account, then it may prefer to give increasing importance to future, as a way to regulate pollution.

Friday, November 6th, 2020 : Stéphane Zuber (CES)

https://zoom.univ-paris1.fr/j/95097295286?pwd=RHNuSjFFUTI5R1VuRVZJRm9ySk5EUT09

Nº de réunion : 950 9729 5286

code secret 491894

Title : Universal social welfare orderings and risk

Abstract : In this paper, we analyze social orderings when there may be a risk on i) the actual allocation people will receive; ii) what the preferences are; and iii) what the size of the population will be. Such risk exist for instance when considering policy that affect future people, for instance climate policy. We show that, in that context there is no satisfactory fair social order- ings that meets minimal requirements of social rationality and respect of people ex ante preferences. We explore three ways to avoid this impossi- bility. First, if the universal social ordering is not an expected utility, we can obtain fair ex ante criteria that replace uncertain individual prospects with a certainty-equivalent measure of well-being. Second, if we drop the Pareto requirement ex ante, we can obtain fair ex post criteria that take an (arbitrary) expected utility of some kind of equally-distributed equivalent level of well-being. Third, if we accept that people well-being is measured by their VNM utility functions, we can construct expected utility social orderings that satisfy of some version of Pareto ex ante.

Friday, October 23rd, 2020 Room 114 : Raouf Boucekine (AMSE)

Title : A dynamic theory of spatial externalities

Abstract : In this paper, we revisit the theory of spatial externalities. In particular, we depart in several respects from the important literature studying the fundamental pollution free riding problem uncovered in the associated empirical works. First, instead of assuming ad hoc pollution diffusion schemes across space, we consider a realistic spatiotemporal law of motion for air and water pollution (diffusion and advection). Second, we tackle spatiotemporal non-cooperative (and cooperative) differential games. Precisely, we consider a circle partitioned into several states where a local authority decides autonomously about its investment, production and depollution strategies over time knowing that investment/production generates pollution, and pollution is transboundary. The time horizon is infinite. Third, we allow for a rich set of geographic heterogeneities across states while the literature assumes identical states. We solve analytically the induced non-cooperative differential game under decentralization and fully characterize the resulting long-term spatial distributions. We further provide with full exploration of the free riding problem, reflected in the so-called border effects. In particular, net pollution flows diffuse at an increasing rate as we approach the borders, with strong asymmetries under advection, and structural breaks show up at the borders. We also build a formal case in which a larger number of states goes with the exacerbation of pollution externalities. Finally, we explore how geographic discrepancies affect the shape of the border effects.

Friday October 16th, 2020 room 114 : Jerôme Renault (TSE)

Title : Long information design

Abstract : We study zero-sum dynamic splitting games between two designers who want to influence the final action of a decision-maker. Each designer controls the public information on a private persistent state: in each period the designers can disclose information to the decision-maker about their own state. Extending tools from repeated games with incomplete information, we study the value and optimal strategies depending on the timing of the game, the possible deadline and the possible restrictions on information revelation. Our analysis covers continuous unconstraint environments, the case where a subset of Blackwell experiments is available to the designers, as well as environments in which designers can only induce finite sets of posterior beliefs. There may be no bound on the number of communication stages required at equilibrium.

Friday, October 9th, 2020 Room S17 : Michel Grabisch (CES)

Title : k-addditive upper approximation of TU-games

Abstract : We study the problem of an upper approximation of a TU-game by a 𝑘-additive game under the con- straint that both games yield the same Shapley value. The best approximation is obtained by minimiz- ing the sum of excesses with respect to the original game, which yields an LP problem. We show that for any game with at most 4 players all vertices of the polyhedron of feasible solutions are optimal, and we give an explicit formula of the value of the LP problem for a particular class of games.

Friday, October 2nd, 2020, Room S17 : Cuong le Van (CES)

Title : Sperner lemma, Fixed Point Theorems, and the Existence of Equilibrium

Abstract : In characterizing the existence of a general equilibrium, existing studies mainly draw on Brouwer and Kakutani fixed point theorems and, to some ex- tent, Gale-Nikaido-Debreu lemma. In this paper, we show that Sperner lemma can play a role as an alternative powerful tool for the same purpose. Specif- ically, Sperner lemma can be used to prove those theorems as well as Gale- Nikaido-Debreu lemma. Additionally, Kakutani fixed point theorem is shown as a corollary of Gale-Nikaido-Debreu lemma. For demonstration on the use of Sperner lemma to prove general equilibrium existence, we consider two com- petitive economies marked either by production goods or financial assets. In each case, without a need to call on the fixed point theorems or Gale-Nikaido- Debreu lemma, we successfully provide a proof on the existence of a general equilibrium solely using Sperner lemma.

Friday, September 25, 2020 Room S17 : Antonin Macé (PSE)

Title : Voter Coordination in Large Elections

Abstract : We study the potential for voter coordination in large elections. Drawing on equilibrium analysis and numerical simulations, we compare the three most basic rules for 3-candidate elections, under which voters may vote for exactly one candidate (Plurality Voting), for exactly two candidates (Anti-Plurality) or for one or two candidates (Approval Voting). As well-known since Duverger [1951], Plurality Voting allows for voter coordination, but the election is indeterminate: at least two candidates are plausible winners. By contrast, coordination always fails under Anti-Plurality Voting. We further show that Approval voting always permits coordination when a Condorcet winner exists, and also ensures that, in most cases, only this normatively appealing candidate can be elected. At the heart of our numerical results lies a novel algorithm computing voter best replies in a large election.

Friday, September 18, 2020 Room S17 : Philippe Bich (CES, Université Paris 1)

Title : Noncooperative Foundation of some Bargaining Solutions from Strategic Uncertainty

Abstract : In our paper, we provide a new non cooperative foundation of several bargaining solutions (Nash bargaining solution, Smorodinsky solution), which also permit to unify these notions. We use prudent games, introduced in (bich JET 2019), which incorporates strategic uncertainty and some prudent behavior related to it. Roughly, we explain how a certain type of « prudence » (we will define) induces a certain type of solution.

Google Sites

Report abuse