Centre d'Economie de la Sorbonne, Salle 117
Paolo Siconolfi (Columbia Business School, Columbia University NY)
Title: Lecture on General Equilibrium and Asymmetric Information
Abstract: We consider multi-stage games, where at each stage, players receive private signals about past and current states, past actions and past signals, and choose actions. We fully characterize the distributions over actions, states, and signals that obtain in any (sequential) communication equilibrium of any expansion of multi-stage games, i.e., when players can receive additional signals. We interpret our results as revelation principles. We apply our characterization to bilateral bargaining problems.
Centre d'Economie de la Sorbonne, Salle S/17
Ludovic Renou (Queen Mary University Of London)
Title: Information design in multi-stage games
Abstract: We consider multi-stage games, where at each stage, players receive private signals about past and current states, past actions and past signals, and choose actions. We fully characterize the distributions over actions, states, and signals that obtain in any (sequential) communication equilibrium of any expansion of multi-stage games, i.e., when players can receive additional signals. We interpret our results as revelation principles. We apply our characterization to bilateral bargaining problems.
Centre d'Economie de la Sorbonne, Salle S/17
René Von Den Brink (VU Amsterdam)
Title: Interval Solutions for TU-games (joint work with Osman Palanci and S. Zeynep Alparslan Gok)
Abstract: Standard solutions for TU-games assign to every TU-game a payoff vector. However, if there is uncertainty about the payoff allocation then we cannot just assign a specific payoff to every player. Therefore, in this paper we introduce interval solutions for TU-games which assign to every TU-game a vector of payoff intervals. Since the solution we propose uses marginal vectors of the interval game, we need to apply a difference operator on intervals. Applying the subtraction operator of Moore (1979), we define an interval solution for TU-games, and we provide an axiomatization.
Centre d'Economie de la Sorbonne, Salle TBA
Yonathan Berman (PSE)
Title: Testing the Ergodic Hypothesis: Equilibrium and Wealth Distributions in the United States
Abstract: Classical studies of wealth inequality make the "ergodic hypothesis" that rescaled wealth converges rapidly to a stationary distribution. This allows powerful analytical techniques but constrains models. We test the hypothesis and find it unsupported by data. In a simple model of a growing economy with wealth reallocation, we fit the reallocation parameter to historical United States wealth data. We find negative reallocation, i.e. from poorer to richer, for which no stationary distribution exists. When we find positive reallocation, convergence to the stationary distribution is slow. Both cases invalidate the ergodic hypothesis. Studies which make it should be treated with caution.
Centre d'Economie de la Sorbonne, Salle S/1
Fuad Aleskerov (HSE, Moscow, Russia)
Title: Evaluation of universities, and heterogeneity of higher education system
Abstract. We propose an assesment of universities by their efficiency score gained from modified Data Envelopment Analysis, incorporating universities; heterogeneity. We analyze a heterogeneity of the educational system on the basis of one parameter: input grades of university students. We propose a mathematical model based on the construction of universities' interval order. We use the Hamming distance to evaluate the heterogeneity of the educational system, and the Unified State Examination (USE) scores of Russian students to illustrate the application of the model.
Centre d'Economie de la Sorbonne, Salle S/17
Jana Vyrastekova (Nijmegen University )
Title: Experimental evidence on the supernatural sanctioning hypothesis (joint work with Rosita Verheij)
Abstract: The supernatural sanctioning hypothesis proposes that human prosocial behavior in large groups of strangers could be enforced by the belief in a punishing supernatural entity (D. D. P. Johnson, 2005; D. Johnson & Krüger, 2004; Benjamin Grant Purzycki et al., 2016). Under this hypothesis, prosocial behavior is independent of monitoring and repeated interactions. We extend the consequences of the hypothesis into the realm of moral behavior consistency. Under the supernatural sanctioning hypothesis, we expect that belief in a punishing supernatural entity is less likely associated with moral licensing, and moral behavior is thus more stable under such a belief. We test this hypothesis using incentivized online experiments on the Amazon MTurk platform.
Centre d'Economie de la Sorbonne, Salle S/1
Daniel Karabekyan (HSE, Moscow, Russia)
Title: Manipulability of scoring rules
Abstract : We study manipulability of different voting rules using computer simultation. We consider different possible models including different probabilities of voting situations, measures of manipulability and preference extensions axioms. For each case, 3 to 5 alternatives and up to 100 voters we compare scoring rules and scoring elimination rules and find the least manipulable for each case. While it is impossible to find the best rule for all the cases, in many situations Nanson's and Hare's rules are the least manipulable ones.
No Seminar
Centre d'Economie de la Sorbonne, Salle S/17
Stéphane Gonzalez (GATE L-SE)
Title: Neutral candidates in approval and disapproval vote (joint with Annick Laruelle and Philippe Solal)
Abstract:
In this article, the question is to select the “best” candidates within a set of candidates when voters cast approval-disapproval ternary ballots. That is, three options are offered to voters: casting a vote “in favor”, a “neutral” vote or a vote “against” each candidate. We first review desirable properties that a rule aggregating approval-disapproval ternary ballots should satisfy. We check whether the rules that have been proposed in the literature satisfy them. Then, we provide comparable axiomatizations of three rules: one is the lexicographical extension of the Approval rule for binary ballots; the second is the lexicographical extension of the Disapproval rule for binary ballots; and the third rule eliminates candidates with more opponents and fewer supporters than other candidates.
Centre d'Economie de la Sorbonne, Salle S/17
Dmitry Levando (NRU-HSE, Moscow)
Title: Impossibility of stable equilibrium price (joint with M. Sakharov)
Abstract: We develop a theory of market instability caused by strategic trade with complete information and without outside shocks. We focus on general equilibrium duopoly as a strategic market game with infinite strategies, and explicit pricing mechanism. First order conditions of the game are the 1-st kind integral equations of Fredholm, which have multiple solutions; a solution is a probability distribution (a mixed strategy) that can be approximated only. Impossibility to construct a unique and exact solution imposes a restriction on existence of converging common beliefs of players about actions of each other, on existence of rational expectations. Price fluctuations in the model do not supply any new information, although the market is informationally efficient in the sense of Fama. We demonstrate these effects for Pareto-efficient strategy profiles and allocations. Our result is also related to existence of sun-spot equilibrium, and noise trade.
Centre d'Economie de la Sorbonne, Salle S/17
Title: Bitcoin and Blockchain: What we know and what are still open questions ( avec Hanna Halaburda).
Abstract: TBA
Holydays
Holydays
Centre d'Economie de la Sorbonne, Salle S/17
Georges Zaccour (GERAD,HEC Montréal)
Title: Counterfeiting and Consumer Welfare: A Differential Game Approach (joint with Bertrand Crettez and Naila Hayek)
Abstract: Counterfeiting, which is defined as illegally copying genuine goods with a brand name, is a widespread phenomenon and is imposing a huge cost on owners of trademarks. Yet, consuming counterfeit products is not prosecuted in the UK, whereas it is in Europe or in the USA. Why is it so? In this paper, we look at how the entry of a counterfeiter affects the legal firm's pricing and advertising strategies and profits. The rationale for focusing on price and advertising is in fact straightforward. First, it is probably the high margin, that is, the difference between the price and the (comparatively very low) production cost that makes counterfeiting financially attractive. Second, the high willingness-to-pay by consumers is driven by the brand image or reputation, and this asset is notably built through advertising. Third, public enforcement of property rights is often lax and not all legal firms can afford private enforcement policies.
Our results are as follows: First, we obtain that counterfeiting affects negatively pricing and advertising strategies before and after entry occurs. Second, we show that under no circumstances counterfeiting can be welcomed by a legal firm, that is, for all parameter values, counterfeiting reduces the profits of the owner of the genuine product. Finally, however, we show that there are circumstances under which consumer benefits from this illegal trade (the decrease in the price of the genuine good compensates the decrease in the brand reputation of this good). Such a result can rationalize non fining consumers of fake products.
Centre d'Economie de la Sorbonne, Salle S/17
Pascal Gourdel (Université Paris 1, CES - PSE)
Title: A convex selection theorem with a non separable Banach space (with Nadia Mâagli)
Short Abstract: In a previous paper, we showed that if X is a metric space and is a Banach space, then any lower semicontinuous correspondence with nonempty convex valued such that has either closed or finite dimensional images admits a selection. In a new paper, we extend this result to the case where X is Hausdorff paracompact and perfectly normal topological space. This allows to revisit the pioneer work of Michael and to show that such a property is a characterization of Hausdorff paracompact and perfectly normal topological space. As in our previous paper, we use the concept of peeling for points where the image of the correspondence has a finite dimension. In our new paper, additional techniques are used to encompass the absence of a metric structure.
Centre d'Economie de la Sorbonne, Salle S/17
Cancelled
Centre d'Economie de la Sorbonne, Salle S/17
Nizar Allouch (University of Kent)
Title: Strategic default in financial networks.
Abstract: This paper investigates a model of strategic interactions in financial networks, where the decision by one agent on whether or not to default impacts the incentives of other agents to escape default. Agents' payoffs are determined by the clearing mechanism introduced in the seminal contribution of Eisenberg and Noe (2001). We first show the existence of a Nash equilibrium of this default game. Next, we develop an algorithm to find all Nash equilibria that relies on the financial network structure. Finally, we explore some policy implications to achieve efficient coordination.
Centre d'Economie de la Sorbonne, Salle S/1
Paola Labrecciosa (Monash University)
Title: Dynamic Price Competition with Reference-Price Effects (joint work with Luca Colombo)
Abstract: We propose a continuous-time model of price competition with horizontally differentiated products and reference-price effects. Consumers have memory of past prices, which they use to form reference prices. For each product variety, consumers compare the observed price with the reference price they have in mind. If the actual price is below (above) the reference price, consumers will perceive a gain (loss). We consider both symmetric and asymmetric reference-price effects. For both cases, we provide an analytical characterization of closed-loop (feedback) Nash equilibrium strategies. We show that, in the presence of symmetric reference-price effects, an increase in the magnitude of reference-price effects (or an improvement in consumers' price memory), makes firms price more aggressively. When instead consumers are loss-averse, there exists an interval of initial reference prices where, as a result of an increase in the magnitude of reference-price effects, firms keep their prices constant over time. Consumers' loss aversion turns out to be anti-competitive when the initial reference price is high, and pro-competitive otherwise.
Centre d'Economie de la Sorbonne, Salle S/1
Luca Colombo (Deakin University)
Title: On Stackelberg Leadership in Continuous Time (with Paola Labrecciosa )
Abstract: We propose a differential oligopoly game where m Stackelberg leaders and n-m Stackelberg followers are engaged in the exploitation of a common-pool renewable resource over an infinite time horizon. At each point in time, firms sell their harvest in the marketplace at a price that depends on total harvest. We assume that each follower maximizes its discounted sum of profits subject to the Cournot assumption regarding the other firms, and each leader maximizes its discounted sum of profits taking as given the output rates of the other leaders, but explicitly considering the aggregate followers' reaction function. Both leaders and followers use Markovian strategies, i.e. they condition their actions on the current stock. The Cournot model and the classical Stackelberg model [one leader and one (multiple) follower(s)] are nested as special cases: Cournot competition arises when m=n; the classical Stackelberg model can be obtained by setting m=1. The equilibrium concept we use is a generalization of the feedback Stackelberg equilibrium to a multiple leader-follower environment. We consider symmetry within groups, and explore the implications of asymmetry between groups for equilibrium strategies and efficiency. In sharp contrast to “static” oligopoly theory, we show that the Cournot equilibrium can be more efficient than the Stackelberg equilibrium. This holds true in the short-run, at the steady-state, and in terms of discounted welfare.
Centre d'Economie de la Sorbonne, Salle S/17
Stéphane ZUBER (CNRS, C.E.S. Université Paris 1 Panthéon-sorbonne and PSE)
Title: Intergenerational equity under catastrophic climate change (with M. Fleurbaey, A. Méjean et A. Pottier)
Abstract:
Climate change raises the issue of intergenerational equity. As climate change threat- ens irreversible and dangerous impacts, possibly leading to extinction, the most relevant trade-off may not be between present and future consumption, but between present con- sumption and the mere existence of future generations. To investigate this trade-off, we build an integrated assessment model that explicitly accounts for the risk of extinction of future generations. We compare different climate policies, which change the probability of catastrophic outcomes yielding an early extinction, within the class of variable population utilitarian social welfare functions. We show that the risk of extinction is the main driver of the preferred policy over climate damages. We analyze the role of inequality aversion and population ethics. Usually a preference for large populations and a low inequality aversion favour the most ambitious climate policy, although there are cases where the effect of in- equality aversion is reversed.
Centre d'Economie de la Sorbonne, Salle S/17
Renaud FOUCARD (Humboldt University, School of Business and Economics)
Title: The political economy of climate policy (with Robert Schmidt)
Abstract:
We analyze climate policy in the context of a potential catastrophe using a simple electoral competition framework. Two parties with both office and policy motivation compete for office by announcing their climate policy, after receiving private signals about the state of the world. We identify an equilibrium in which both parties truthfully reveal their private information to the voters and the implemented policy is (almost) first-best for all possible realizations of parties’ signals. In this asymmetric equilibrium one party adopts extreme platforms, while the other party adopts moderate ones. The equilibrium exists if the moderate party is sufficiently policy-motivated.
Centre d'Economie de la Sorbonne, Salle S/17
Marc-Arthur DIAYE (University of Paris 1)
Title: Do Performance Appraisals Decrease Employees' Psychosocial Risks? (with Rahma DALY)
Abstract: Performance appraisals are among the most widely used managerial practices. Its effects on economic variables like wage and productivity have been investigated in the literature. In this paper, we use a French matched employer-employee data (French Working Conditions Survey 2013), in order to assess the effect of performance appraisals on employees' psychosocial risks. We show that this effect is negative, which means that performance appraisals reduce workers' psychosocial risks.
Centre d'Economie de la Sorbonne, Salle S/17
Okay Gunes (University of Paris 1)
Title: Hedonic Recommendation: An Econometric Application
Abstract: This paper shows an example of how economic theory can be applied to big data analysis. To this end, two layers of machine learning using econometric models are introduced into the recommender system. The motivation is that traditional recommendation approaches are biased due to ignoring final preference order of each individual and to under-specification of the interaction between the socio-economic characteristic of the participants and the characteristics of the commodities. In this respect, our hedonic recommendation approach proposes first to correct the inner preferences with respect to the tastes of each individual and the characteristics of given products. In the second layer, the relative preferences among participants are predicted through their socio-economic characteristics. The robustness of the model is tested with the MovieLens (100k data consists of 943 users on 1682 movies) from a movie recommendation website which is run by GroupLens, a research lab at the University of Minnesota. According to direct prediction results from the original data, mean absolute errors and mean squared errors for Cosine(vector-based) similarity are (0.829 and 1.070), for Singular Value decomposition (SVD) are (2.634 and 8.396) by minimizing with Stochastic Gradient Descent are (0.808 and 1.118) and for Alternating Least Squares Method are (1.139 and 2.369) while Hedonic recommendation approach gives (0.600 and 0.837), (1.908 and 4.562), (0.693 and 0.834) and (0.805 and 0.949) respectively which indicates an important improvement of the recommender system.
Centre d'Economie de la Sorbonne, Salle S/17
Federica Ceron (University of Paris 1)
Title: Aggregation of Bayesian preferences: Unanility vs Monotonicity.
Abstract:
This article reconsiders the issue of Bayesian aggregation by pointing at a conflict that may arise between two logically independent dominance criteria, Pareto dominance and statewise dominance, that are commonly imposed on social preferences. We propose a weaker dominance axiom that restricts statewise dominance to Pareto dominant alternatives and Pareto dominance to statewise dominant alternatives. The associated aggregation rule is a convex combination of two components, the first being a weighted sum of the individuals’ subjective expected utility (SEU) functional, the second being a social SEU functional, with associated social utility function and social belief. Such representation establishes the existence of a trade off between adherence to the Pareto principle and compliance with statewise dominance. We then investigate what are the consequences of adding to our assumptions either of the two dominance criteria in their full force and obtain that each of them is equivalent to discarding the other, unless there is essentially a common prior probability