The testable implications of zero-sum games

We study collective choices from the revealed preference theory viewpoint. For every product set of individual actions, joint choices are called Nash-rationalizable if there exists a preference relation for each player such that the selected joint actions are Nash equilibria of the corresponding game. We characterize Nash-rationalizable joint choice behavior by zero-sum games, or games of conflicting interests. If the joint choice behavior forms a product subset, the behavior is called interchangeable. We prove that interchangeability is the only additional empirical condition which distinguishes zero-sum games from general non-cooperative games.     

Strong Nash equilibrium in games with common and complementary local utilities

A rather general class of strategic games is described where the coalitional improvements are acyclic and hence strong Nash equilibria exist: The players derive their utilities from the use of certain facilities; all players using a facility extract the same amount of local utility therefrom, which amount depends both on the set of users and on their actions, and is decreasing in the set of users; the ultimate utility of each player is the minimum of the local utilities at all relevant facilities. Two important subclasses are “games with structured utilities,” basic properties of which were discovered in 1970s and 1980s, and “bottleneck congestion games,” which attracted researchers’ attention quite recently. The former games are representative in the sense that every game from the whole class is isomorphic to one of them. The necessity of the minimum aggregation for the existence of strong Nash equilibria, actually, just Pareto optimal Nash equilibria, in all games of this type is established.     

The women of Cairo: Equilibria in large anonymous games

In this article, I characterize Nash equilibria of large anonymous games by providing the following neccessary and sufficient condition for an equilibrium distribution: for no subset K of actions more players play actions in K than have a best response in K to the given distribution. While neccessity is trivial the proof for sufficiency relies on a theorem by [Math. Proc. Camb. Philos. Soc. 78 (1974) 323] which is an extension of Hall’s theorem or the marriage lemma well known from graph theory. The veiling problem for the women of Cairo serves as an illustrating heuristic example explaining the nature of the result.     

Global recessions as a cascade phenomenon with interacting agents

This paper examines global recessions as a cascade phenomenon. In other words, how recessions arising within one or more countries might percolate across a network of connected economies. An agent based model is set up in which the agents are Western economies. A country has a probability of entering recession in any given year and one of emerging from it the next. In addition, the agents have a threshold propensity, which varies across time, to import a recession from the agents most closely connected to them. The agents are connected on a network, and an agent’s neighbours at any time are either in (state 1) or out (state 0) of recession. If the weighted sum exceeds the threshold, the agent also goes into recession. Annual real GDP growth for 17 Western countries 1871–2006 is used as the data set. The model is able to replicate three key features of the statistical distribution of recessions: the distribution of the number of countries in recession in any given year, the duration of recessions within the individual countries, and the distribution of ‘wait time’ between recessions i.e. the number of years between them. The network structure is important for the interacting agents to replicate the stylised facts. The country-specific probabilities of entering and emerging from recession by themselves give results which are by no means as well matched to the actual data. We are grateful to an anonymous referee for some extremely helpful comments.     

The Theory of Socially Embedded Games: The Mathematics of Social Relationships,Rule Complexes,and Action Modalities

In their classic work, Von Neumann and Morgensterndefined a game as simply the totality of the rules which describe it. Theydid not, however, elaborate a theory of rules. Such considerations lead toconceptualizing rules and rule configurations as mathematical objects, specifyingthe principles for combining rules, developing the theory of revising,replacing, and, in general transforming rules and rule complexes. Themathematics is based on contemporary developments at the interface ofmathematics, logic, and computer science. This article, drawing on themathematical theory of rules and rule complexes, extends and generalizes gametheory (GGT). The theory of rule complexes is used to conceptualize andanalyze diverse social relationships, roles, and games as particulartypes of rule complexes. A social role, for instance, is the major basisof an individual's action in a game. It consists of at least four majorcomponents – which are mathematical objects – in the determinationof action: value complex, model of reality (including beliefs and knowledgebases), a repertoire of acts, routines, programs, and strategies, and modalities,role-specific algorithms for determininig or generating action in gamesettings. The article focuses on three types of action modality routineor habitual, normative, andinstrumental modalities. The theory: (1) provides a cultural/institutionalbasis for a theory of gameswhere games, social relationships, and rolesare formalized in terms of rule complexes; (2) explains human action as a formof rule application or rule-following action, which underlies allmodalities of action; (3) formulates the theory that actors construct an action or make choices amongalternative actions by making comparisons and judging similarity (ordissimilarity) between an option or options considered and their norms and values,and, in general, determine whether or not, and to what degree, a value,norm, or goal will be realized or satisfied; (4)reconceptualizes ``game' as a social form and makes a distinction between open and closed games.     

Multilateral negotiations and formation of coalitions

This paper analyses properties of games modeling multilateral negotiations leading to the formation of coalitions in an environment with widespread externalities. The payoff generated by each coalition is determined by an exogenous partition function (the parameter space). We show that in almost all games, except in a set of measure zero of the parameter space, the Markov perfect equilibrium value of coalitions and the state transition probability that describe the path of coalition formation is locally unique and stable. Therefore, comparative statics analysis are well-defined and can be performed using standard calculus tools. Global uniqueness does not hold in general, but the number of equilibria is finite and odd. In addition, a sufficient condition for global uniqueness is derived, and using this sufficient condition we show that there is a globally unique equilibrium in three-player superadditive games.     

Cournot vs. Walras: A reappraisal through simulations

Best-reply behavior in Cournot oligopolies generally leads to Cournot-Nash equilibrium, but imitative behavior selects the Walrasian equilibrium as the unique stochastically stable state. Previous work (Alós-Ferrer, 2004) showed that in the presence of memory, imitative behavior leads to a non-trivial dynamics selecting all quantities between the Cournot and Walrasian outcomes. However, the scope of previous results was limited to specific assumptions on demand and cost functions, and did not provide information on the shape of the distribution of outcomes. We use computational simulations to address these limitations. We show that the selection result for non-trivial memory holds beyond the set of well-behaved Cournot games previously analyzed. Further, we find that, in Cournot games, the limit distribution of long-run outcomes is highly skewed towards the Walrasian quantity. Although longer memory increases the importance of the Cournot equilibrium, the competitive outcome remains the dominant prediction.     

信息网络系统在中国第十一届全运会气象服务中的应用

信息网络系统是整个十一运会气象服务的信息交换平台,其主要目标采用先进的网络技术,提高数据融合、分析和综合处理能力,建立与十一运会气象服务网站、预报预测系统和气象服务信息分发系统要求相适应的数据环境,提高气象信息的综合管理水平,该系统将重点解决整个系统的连接以及内外部信息的收集、存储、交换、分发以及系统的集中统一控制和管理等问题。     

Communication equilibria with partially verifiable types

This paper studies the set of equilibria that can be achieved by adding general communication systems to Bayesian games in which some information can be certified or, equivalently, in which players’ types are partially verifiable. Certifiability of information is formalized by a set of available reports for each player that varies with the true state of the world. Given these state-dependent sets of reports, we characterize canonical equilibria for which generalized versions of the revelation principle are valid. Communication equilibria and associated canonical representations are obtained as special cases when no information can be certified.     

Piecewise closed-loop equilibria in differential games with regime switching strategies

We propose a new methodology exploring piecewise closed-loop equilibrium strategies in differential games with regime switching actions. We develop a general game with two players. Players choose an action that influences the evolution of a state variable, and decide on the switching time from one regime to another. Compared to the optimal control problem with regime switching, necessary optimality conditions are modified for the first player to switch. When choosing her optimal switching strategy, this player considers the impact of her choice on the other player’s actions and consequently on her own payoffs. In order to determine the equilibrium timing of regime changes, we derive conditions that help eliminate candidate equilibrium strategies that do not survive deviations in switching strategies. We then apply this new methodology to an exhaustible resource extraction game.     

Strategic behavior in non-atomic games

In order to remedy the possible loss of strategic interaction in non-atomic games with a societal choice, this study proposes a refinement of Nash equilibrium, strategic equilibrium. Given a non-atomic game, its perturbed game is one in which every player believes that he alone has a small, but positive, impact on the societal choice; and a distribution is a strategic equilibrium if it is a limit point of a sequence of Nash equilibrium distributions of games in which each player’s belief about his impact on the societal choice goes to zero. After proving the existence of strategic equilibria, we show that all of them must be Nash. We also show that all regular equilibria of smooth non-atomic games are strategic. Moreover, it is displayed that in many economic applications, the set of strategic equilibria coincides with that of Nash equilibria of large finite games.     

Weakly rational expectations

Aumann and Drèze (2008) characterised the set of interim expected payoffs that players may have in rational belief systems, in which there is common knowledge of rationality and a common prior. We show here that common knowledge of rationality is not needed: when rationality is satisfied in the support of an action-consistent distribution (a concept introduced by Barelli (2009)), one obtains exactly the same set of rational expectations, despite the fact that in such ‘weakly rational belief systems’ there may not be mutual knowledge of rationality, let alone common knowledge of rationality. In the special case of two-player zero-sum games, the only expected payoff is the minmax value, even under these weak assumptions.     

Semiparametric estimation of Markov decision processes with continuous state space

We propose a general two-step estimator for a popular Markov discrete choice model that includes a class of Markovian games with continuous observable state space. Our estimation procedure generalizes the computationally attractive methodology of Pesendorfer and Schmidt-Dengler (2008) that assumed finite observable states. This extension is non-trivial as the policy value functions are solutions to some type II integral equations. We show that the inverse problem is well-posed. We provide a set of primitive conditions to ensure root-T consistent estimation for the finite dimensional structural parameters and the distribution theory for the value functions in a time series framework.     

Gradient dynamics in population games: Some basic results

When each player in a population game continuously adjusts her action to move up the payoff gradient, then the state variable (the action distribution) obeys a nonlinear partial differential equation. We find conditions that render gradient adjustment myopically optimal and analyze two broad classes of population games. For one class, we use known results to establish the existence and uniqueness of solutions to the PDE. In some cases, these solutions exhibit shock waves or rarefaction waves. For a second class, we use a local form of Nash equilibrium to characterize the steady state solutions of the PDE and find sufficient conditions for asymptotic convergence.     

Delay,multiplicity, and non-existence of equilibrium in unanimity bargaining games

We consider a class of perfect information bargaining games with unanimity acceptance rule. The proposer and the order of responding players are determined by the state that evolves stochastically over time. The probability distribution of the state in the next period is determined jointly by the current state and the identity of the player who rejected the current proposal. This protocol encompasses a vast number of special cases studied in the literature. We show that subgame perfect equilibria in pure stationary strategies need not exist. When such equilibria do exist, they may exhibit delay. Limit equilibria as the players become infinitely patient need not be unique.     

Coalitional games with veto players: Consistency, monotonicity and Nash outcomes

Following Dagan et al. [Dagan, N., Volij, O., Serrano, R. (1997). A non-cooperative view on consistent bankruptcy rules, Games Econ. Behav. 18, 55–72], we construct an extensive form game for veto-balanced TU games in which a veto player is the proposer and the other players are responders. The set of Nash outcomes of this extensive form game is described, and compared to solutions of TU games such as the nucleolus, kernel and egalitarian core. We find necessary and sufficient conditions under which the nucleolus of the game is a Nash outcome.     

Measuring trustworthiness of information diffusion by risk discovery process in social networking services

Most of current social network services are vulnerable to malicious actions. For example, rumor (e.g., contaminated and distorted information) can be diffused along the social links. In this paper, given a social network service, we design a peer-to-peer (P2P) network, and propose a robust information diffusion model to efficiently detect the malicious peers from which a risk (i.e., rumor) has been generated on the P2P network. Thereby, by aggregating social interactions among users, a set of interaction sequences are obtained. Given a set of interaction sequences, statistical sequence mining method is exploited to discover a certain social position which provides peculiar patterns on the P2P networks. For evaluating the proposed method, we conducted two experimentations with NetLogo simulation platform for risk discovery on social network.     

The core of the inductive limit of a direct system of economies with a communication structure

This paper studies direct systems of finite, that is with finitely many agents, communication structures, finite (balanced and superadditive) NTU games and finite economies. The inductive limit of such a system is again a communication structure, an NTU game or an economy, this time possibly with infinitely many agents. As a matter of fact, each infinite communication structure, each infinite NTU game and each infinite economy, is the inductive limit of a direct system of finite communication structures, finite NTU games and finite economies. A communication game is an NTU game with a communication structure on the set of players. To each economy, there corresponds a balanced and superadditive NTU game. To each economy with a communication structure on the set of agents, there corresponds a communication game. In the paper it is proved that the core of the inductive limit of a direct system of communication games is not empty and in fact the intersection of the cores of the finite communication games of the direct system. It follows that each infinite economy (with or without a communication structure on the set of agents) has a nonempty core. A direct system of economies is a generalisation of the Debreu and Scarf [Debreu, G., Scarf, H. A limit theorem on the core of an economy, International Economic Review 4, pp. 235–246.] example of `replica economies'. The proof of the nonemptiness of the core of the inductive limit of a direct system of economies is along the lines of the proof by Debreu and Scarf. As by-product it is shown that an NTU game is totally balanced if and only if all its finite subgames are balanced.     

The value of information: The case of signal-dependent opportunity sets

We generalize the economic decision problem considered by Blackwell (1953) in which a decision-maker chooses an action after observing a signal correlated to the state of nature. Unlike Blackwell's case where the feasible set is fixed, in our framework the feasible set of actions depends on the signal and the information system. We argue that such a framework has more significance to economic models. As was demonstrated by Hirshleifer (1971) in such cases, contrary to Blackwell's well-known result, more information may be disadvantageous. We derive conditions for this general model which guarantee that more information is beneficial.