Friday 26 Juin 14h-15h
On zoom : https://pantheonsorbonne.zoom.us/j/92308616618?pwd=Zkhsazd2d3AySWpudE5jNGw2aG80UT09
Alfonso Montes (Ecole polytechnique)
Title : Canonical Equilibria in Games with Flexible Information Acquisition
Abstract: I study costly information acquisition by multiple decision-makers facing a strategic environment. First, each agent chooses an arbitrary signal about the state of nature, and she incurs in a cost that is increasing in the amount of information contained in the signal. Then, once information has been acquired, agents choose their actions in a Bayesian game. I show that for every equilibrium there exists an equivalent pure strategy Bayes Nash equilibrium in which the space of signals is equal to the action space. The existence of such equilibrium, which I call canonical equilibrium, provides a revelation principle for games with flexible information acquisition. I also prove existence of equilibrium, and I extend some results from single-agent costly information acquisition to strategic environments.
Friday 19 Juin 11h-12h
On zoom : https://pantheonsorbonne.zoom.us/j/92308616618?pwd=Zkhsazd2d3AySWpudE5jNGw2aG80UT09
Giacomo Weber (PSE)
Title : Clustering and Analogy-Based Expectation Equilibrium with an Application to Moral Hazard in Team (co-authored by P. Jehiel)
Abstract: We combine together the notion of Analogy-based Expectation Equilibrium (ABEE) and the K-means clustering algorithm. ABEE is a bounded rationality equilibrium notion that tackles cognitive rationality: players form beliefs bundling games together, the collection of these bundles for a player is called analogy partition. Bundles are primitives in the ABEE original framework; behavior is endogenous. K-means is a machine learning problem of unsupervised learning. K-means algorithm is typically used to identify underlying structure in data, forming classes (clusters). Therefore, data is a primitive; while bundling is endogenous.
Both concepts aggregate data. In ABEE, data is about players’ behavior. Our objective is to endogenize the way players bundle games in the ABEE in the spirit of K-means. Thus, both bundles and behavior are endogenous. We provide a mixed extension of a strategic environment to ensure existence of stable analogy partitions. We apply this concept of stability to families of Moral Hazard in team interactions. When there are strategic complementaries, we find multiple stable ABEE. Instead, under strategic substitutability, sometimes stable ABEE can be found only in the mixed extension.
Friday 5 June 11h-12h
On zoom : https://pantheonsorbonne.zoom.us/j/4082032946?pwd=MFN6YW4wZENzZDhUWVlZWmtpSUgwdz09
Fei Xu (Science Po Paris)
Title : An Economic Model of Bribery and Anti-Corruption Measures
Abstract : In this paper, we are concerned with the corruption of government officials---individually or in the context of a committee---in a framework of bribes and anti-corruption measures. Unlike most of the literature, we propose a model that integrates three types of agents: The government (or regulator), the officers, and the donor. We prove the existence of the Nash-equilibrium over the space of the bribe and anti-corruption measure. Then, we provide some comparative statics results for changes in salaries, monitoring, and the probability of detection. Salary increases may be nullified by changes in the bribe and the anti-corruption measure. Because of the involved gains of corruption, our model shows that some government bodies may be marred by entrenched corruption even in countries with the highest levels of transparency and effectiveness, whereas petty bribes may be pervasive in countries with fragile institutions.
Friday 29 Mai 11h-12h
On zoom : https://pantheonsorbonne.zoom.us/j/4082032946?pwd=MFN6YW4wZENzZDhUWVlZWmtpSUgwdz09
Tobias Rachidi (Universität Bonn)
Title : Committee Search: Evaluating One or Multiple Candidates at a Time? (joint with Christina Luxen)
Abstract : This paper studies committee search where members either assess candidates "one at a time", i.e., on a rolling basis, or they simultaneously evaluate in each time period a set of candidates of fixed size. The former search procedure has been studied before, whereas the exploration of the latter search technology is novel in the committee search literature. We compare both search procedures in terms of acceptance standards and welfare. Generally, the superiority of one or the other search technology depends on the voting rule and the specification of search costs associated with the simultaneous evaluation of multiple candidates. The adoption of a qualified
majority rule changes the evaluation of search procedures compared to the ranking under the unanimity rule, revealing that the presence of a search committee fundamentally alters the search problem in comparison with the single decision-maker case. This is the main qualitative insight of this paper and we discuss its implications for committee search in practice.
Friday 13 March 12h-13h
Centre d'Economie de la Sorbonne, Salle S/17
Sudipta Sarangi (Virginia Tech)
Title : Network Formation with Multigraphs and Strategic Complementarities
Abstract : This paper examines the formation of one network G when connections in a second network H are inherited under two scenarios: (i) H is asymmetric allowing for a wide range of networks called nested split graphs, and (ii) H is a connected regular graph. The bulk of our paper assumes that both G and H are interdependent because the respective actions in each are (weak) strategic complements. This complementarity creates a silver spoon effect whereby those who inherit high Katz-Bonacich centrality in H will continue to have high Katz-Bonacich centrality in G. There is, however, a silver lining: depending on the costs of link formation, the formed network G may allow for an improvement in centrality. As an application, we introduce an overlapping generations models to analyze intergenerational social mobility. We show that the silver spoon effect persists across generations with descendants of agents who are highly connected continuing to remain highly connected. Finally, we explore the implications of actions being strategic substitutes across networks. This can lead to an outcome where well-connected agents in H establish no links in G, and those with no connections in H form all the links in G. Our analysis provides insight into preferential attachment, how asymmetries in one network may be magnified or diminished in another, and why players with links in one network may form no links in another network.
Friday 6 March 12h-13h
Centre d'Economie de la Sorbonne, Salle S/17
Anna Zseleva (Tel Aviv University)
Title : Existence of justifiable equilibrium (joint work with János Flesch and Dries Vermeulen)
Abstract :
We present a general existence result for a type of equilibrium in normal-form games, which extends the concept of Nash equilibrium. We consider nonzero-sum normal-form games with an arbitrary number of players and arbitrary action spaces. We impose merely one condition: the payoff function of each player is bounded. We allow players to use finitely additive probability measures as mixed strategies.
Since we do not assume any measurability conditions, for a given strategy profile the expected payoff is generally not uniquely defined, and integration theory only provides an upper bound, the upper integral, and a lower bound, the lower integral. A strategy profile is called a justifiable equilibrium if each player evaluates this profile by the upper integral, and each player evaluates all his possible deviations by the lower integral. We show that a justifiable equilibrium always exists.
Our equilibrium concept and existence result are motivated by Vasquez (2017), who defines a conceptually related equilibrium notion, and shows its existence under the conditions of finitely many players, separable metric action spaces and bounded Borel measurable payoff functions. Our proof borrows several ideas from Vasquez (2017) , but is more direct as it does not make use of countably additive representations of finitely additive measures by Yosida and Hewitt (1952).
Friday 28 February 12h-13h
Centre d'Economie de la Sorbonne, Salle S/17
Philipp Sadowski (Duke university)
Title : An Evolutionary Perspective on Updating Risk and Ambiguity Preferences
Abstract : Using an approach based on evolution and adaptation, we provide foundations for a model of choice under uncertainty based on adaptive preferences, and we show that updating of those preferences in response to new information will respect dynamic consistency even at the cost of violating consequentialism. We argue that our approach can be applied in most contexts with ambiguity, and we establish that adaptive preferences nest variants of many models in the literature on risk and ambiguity as special cases. Since models of either ambiguity aversion or non-expected utility for risk cannot satisfy both dynamic consistency and consequentialism without strong assumptions on beliefs and information structures, our results add a novel perspective to the discourse about which of these properties should be maintained in applications. In addition, a central feature of adaptive preferences and the models they nest is a tight connection between ambiguity attitudes and violations of expected utility in the context of risk.
Friday 14 February 12h-13h
Centre d'Economie de la Sorbonne, Salle S/17 (Cancelled)
Cuong Tran (Université Paris 1)
Title : Shocks of productivity in economies
Abstract : In this paper, the economies with the shocks of the productivity are studied. Consumers are considered in the continuum case in which they deal with endowment shocks of individual labour and also face the borrowing conditions. Competitive equilibrium are shown in term of sequence of aggregate distributions.
Friday 7 February January 12h-13h
Centre d'Economie de la Sorbonne, Salle S/17
Stefano Moretti (Dauphine University)
Title : Some interesting families of Generalized Additive Games and their characterizations (based on a joint work with Henk Norde, Tilburg University)
Abstract : Generalized additive games (GAGs) are Transferable Utility (TU) games where the worth of any coalition of players can be computed as a sum of individual contributions. A basic ingredient for GAGs is the so-called coalitional map, that specifies the set of friends (or contributors) of a coalition S. Given a coalitional map and a vector of n nonnegative real numbers representing the individual contribution of players, the associated GAG assigns to every coalition S the sum of the contributions over the set of friends of S.
In this paper we study the effect of the combination of four properties for coalitional maps on the associated GAGs corresponding to any vector of nonnegative individual contributions. To be more specific, the first property we introduce is a monotonicity condition: a coalitional map is said monotonic if the friends of any coalition S are also friends of any coalition T containing S. Differently, a coalitional map is said proper if any two disjoint coalitions S and T, have no friends in common. The third property deals with the veto-behaviour of players. More precisely, a coalitional map is said veto-rich if for any player i, either i is not a friend of any coalition, or i is a friend of the grand coalition and, at the same time, the intersection of coalitions having i as a friend is non-empty. Finally, a coalitional map is supermodular if the intersection of the set of friends of two coalitons S and T coincides with the set of friends of their intersection.
We first prove that these properties for coalitional maps characterize some interesting classes of GAGs that satisfy properties for TU-games, like monotonicity, superadditivity, (total) balancedness, population monotonic allocation scheme (pmas)-admissibility and supermodularity, for all nonnegative vectors of individual values.
Then, we use these characterizations to analyse several classes of TU games from the literature, with a particular focus on Operations Research games. In particular, we consider (weighted) glove games, (generalized) airport games, fixed tree games, link-connection games, “simple” minimum cost spanning tree games and (weighted) colouring games.
Friday 31 January 12h-13h
Centre d'Economie de la Sorbonne, Salle S/17
Matias Fuentes (National University of San Martín)
Title : Essential equilibria in large square economies
Abstract : Exchange economies are defined by a mapping between an atomless space of agents and a space of characteristics where the commodity space is a separable Banach space. We characterize equilibrium stability of economies relaying on the continuity of the equilibrium correspondence. We provide a positive answer to an open question about the continuity of the Walras correspondence in infinite dimensional spaces. In addition, we do not assume neither differentiability nor a fixed set of agents for the different economies, like it is usually assumed in the stability literature.
Friday 24 January, 12h-13h
Centre d'Economie de la Sorbonne, Salle S/17
Paola Labrecciosa (Monash University)
Title: Industry-wide learning in differentiated oligopoly (joint with Luca Colombo)
Abstract: We develop a continuous-time game of oligopolistic competition accounting for industry-wide learning and organizational forgetting. Firms compete either in prices or in quantities. Our solution concept is Markov Perfect Equilibrium (MPE). We address questions new to the oligopoly and the learning curve literatures, and find an array of novel results.
Friday 17 January, 12h-13h
Centre d'Economie de la Sorbonne, Salle S/17
Luca Colombo (Deakin University)
Title: A Dynamic Analysis of Pollution Abatement with Endogenous Number of Contributors: Loose vs Tight Cooperation (joint with Paola Labrecciosa and Ngo Van Long)
Abstract: We propose a dynamic model of pollution abatement in which the number of contributors is endogenous and thus may differ between two modes of cooperation, namely, loose vs tight. In the tight mode of cooperation, each member is prescribed a specific target, whereas in the loose one, members choose their own abatement levels as Nash players. Conditions exist such that the incentive to free ride is lower and the number of contributors is higher in the loose cooperation framework, and this can lead to higher welfare, both in the steady state and along the transition path. Paradoxically, in each mode of cooperation, an increase in the number of contributors may result in a higher stock of pollution in the long run.
Friday 20 December 12h-13h
Centre d'Economie de la Sorbonne, Salle 114
Francesca Larosa (University of Venice )
Title : Mapping innovation for climate change adaptation: a network approach
Abstract :
Climate services are technology-intensive, science-based and user-tailored tools providing timely climate information to a wide set of users. They accelerate innovation, while contributing to societal adaptation. Research has explored the advancements of climate services in multiple fields, producing a wealth of interdisciplinary knowledge ranging from climatology to the social sciences. The aim of this paper is to map the global landscape of research on climate services and to identify patterns at individual, affiliation and country level and the structural properties of each community. We use a sample of 358 records published between 1974 and 2018 and quantitatively analyze them. We provide insights into the main characteristics of the community of climate services through Bibliometrics and complement these findings with Network Science. We have computed the centrality of each actor as derived from a Principal Component Analysis of 42 different measures. By exploring the structural properties of the networks of individuals, institutions and countries we derive implications on the most central agents. Furthermore, we detect brokers in the network, capable of facilitating the information flow and increasing the cohesion of the community. We finally analyze the abstracts of the sample via Content Analysis. We find a progressive shift towards climate adaptation and user-centric visions. Agriculture and Energy are the top mentioned sectors. Anglophone countries and institutions are quantitatively dominant, and they are also important in connecting different discipline of the network of scholars, by building on established partnerships. Finding that nodes facilitating the diffusion of information flows (the brokers) are not necessarily the most central, but have a high degree of interdisciplinarity facilitating interactions of different communities.
Friday 13 December 12h-13h
Centre d'Economie de la Sorbonne, Salle 114
Jérôme Renault (TSE- Université Toulouse 1 Capitole)
Title : Long Information Design (joint with F Koessler, M. Laclau et T. Tomala )
Abstract :
We study competitive information design 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. Using tools from repeated games with incomplete information on both sides, we study the value and optimal strategies depending on the timing of the game, the possible deadline and the possible restriction over the sets of possible splittings. Our analysis covers continuous environments as well as environments in which designers can only induce finite sets of posterior beliefs: in the latter framework, there may be no bound on the number of communication stages required at equilibrium.
Friday 06 December 12h-13h :
Centre d'Economie de la Sorbonne, Salle 114
Christina Pawlowitsch (Université Panthéon-Assas, LEMMA )
Title : The evolutionary dynamics of costly signaling (joint with Joseph Hofbauer)
Abstract :
Costly-signaling games have a remarkably wide range of applications, from education as a costly signal in the job market over handicaps as a signal for fitness in mate selection to politeness in language. While the use of game-theoretic equilibrium analysis in such models is often justified by some intuitive dynamic argument, the formal analysis of evolutionary dynamics in costly-signaling games has only recently gained more attention. In this paper, we study evolutionary dynamics in two basic classes of games with two states of nature, two signals, and two possible reactions in response to signals: a discrete version of Spence's (1973) model and a discrete version of Grafen's (1990) formalization of the handicap principle.
We first use index theory to give a rough account of the dynamic stability properties of the equilibria in these games. Then, we study in more detail the replicator dynamics and to some extent the best-response dynamics. We relate our findings to equilibrium analysis based on classical, rationality-oriented methods of equilibrium refinement in signaling games.
Friday 29 November 12h-13h
Centre d'Economie de la Sorbonne, Salle 114
Norio Takeoka (Hitotsubashi University )
Title : Information acquisition with subjective waiting costs
Abstract :
Information acquisition is an important aspect of decision making. Acquiring information is costly, as in the literature of rational inattention, but the cost of infor- mation acquisition is not typically observable and hence it is not obvious how it can be measured. Using preference over menus, de Oliveira, Denti, Mihm, and Ozbek (2017) provide an axiomatic foundation for the additive costs model of information acqui- sition. On the other hand, if obtaining signals from experiments is time-consuming, such as in the case of a long-run investment decision, costs may be measured as a discount factor or waiting time for acquiring information. We provide an axiomatic foundation for such an alternative model and identify unique discounting costs.
To prove the main theorem, we borrow techniques from the literature of choice under ambiguity. Our representation has a parallel relationship with the confidence representation of Chateauneuf and Faro (2009). We first show, as an intermediate lemma, that our axioms ensure a counterpart of the uncertain averse representation of Cerreia-Vioglio, Maccheroni, Marinacci, and Montrucchio (2011) and then specialize it into the confidence-class representation.
Friday 22 November 12h-13h
Centre d'Economie de la Sorbonne, Salle 114
Junnan He (Science Po Paris)
Title : Moderate Expected Utility (joint with Paulo Natenzon )
Abstract : The moderate utility model represents the probability of choosing an option in a pairwise comparison as an increasing function of utility difference divided by a dissimilarity metric. We provide a single, directly testable property that characterizes the model: choices are moderately transitive. We show that the model allows the analyst to accommodate well-known failures of strong transitivity, while retaining significantly more empirical bite than weak transitivity, achieving a useful compromise. Extending the analysis to the domain of risky choice, we introduce and characterize the moderate expected utility model, and we show how the analyst can measure utility and dissimilarity from observed choice behavior.
Friday 15 November 12h-13h
Journée du CES
Friday 8 November 12h-13h
Centre d'Economie de la Sorbonne, Salle 114
Mehmet Ismail (Kings College London)
Title : The story of conflict and cooperation
Abstract : The story of conflict and cooperation has started millions of years ago, and now it is everywhere: In biology, computer science, economics, political science, and psychology. Examples include wars, airline alliances, trade, oligopolistic cartels, the evolution of species and genes, and team sports. However, neither cooperative games nor noncooperative games---in which each player acts independently without collaboration with any of the others---fully capture the competition between and across individuals and groups, and the strategic partnerships that give rise to such groups. Thus, one needs to extend the noncooperative framework to study strategic games like scientific publication, which is a rather competitive game, yet (strategic) collaboration is widespread. In this paper, I propose a novel way to rationally play games of conflict and cooperation under the Principle of Free Will---players are free to cooperate to coordinate their actions or act independently.
Friday 25 October 12h-13h
Centre d'Economie de la Sorbonne, Salle 114
Julio Davila (CNRS-Université Paris 1)
Title : Property rights and long-run capital
Abstract : The fact that some proprietary capital gradually falls into the public domain (e.g. patents) or is taxed to fund productive public spending (e.g. public infrastructures and the institutional framework) inefficiently decreases capital accumulation, impacting households’ consumption. Specifically, for a neoclassical infinitely-lived agents economy with constant returns to scale the planner’s steady state consumption is 4.6%-9.1% higher than the market one —for standard empirically supported parameters. For a similarly parametrised overlapping generations economy it is around 10.5%. A tax and subsidy balanced policy able to decentralise the planner’s steady consists of (i) subsidising the rental rate of private capital by an amount equal to its depreciation by (ii) taxing households’ net position between, on the one hand, firm and depreciated capital ownership and, on the other, borrowing against future dividends and its resale value. From standard functions and parameterisations of the OG setup it follows that the savings rate decentralising the planner’s steady state is close to 61.5% —of which 1/3 in loans to firms and 2/3 in real monetary balances and assets ownership net of borrowing against the latter and that the tax rate on household net debt is smaller the bigger are monetary real balances and debt.
Friday 18 October 12h-13h
Centre d'Economie de la Sorbonne, Salle 114
Luciano Campi (London School of Economics)
Title : Correlated equilibria and mean field games
Abstract : Mean field games are limit models for symmetric N-player games, as N tends infinity, where the pre-limit models are solved in terms of Nash equilibria. A generalization of the notion of Nash equilibrium, due to Robert Aumann (1973, 1987), is that of a correlated equilibrium. Here, we discuss, in a simple non-static setting, the mean field game limit for correlated equilibria. We give a definition of correlated mean field game solution, prove that it arises as limit of N-player correlated equilibria in restricted (”open-loop”) Markov feedback strategies, and show how to construct approximate N-player equilibria starting from a correlated mean field game solution. We also compare our definition to the one by Lacker (2018) of weak solutions for mean field games without a common noise. (Joint work with Markus Fischer, Padua University)