Farsighted strategies in the formation of a communication network

I examine the formation of a specific communication network, a variant of the two-way flow model, in which agents have farsighted strategies. I show that the likelihood to form efficient networks tends to zero for sufficiently large network sizes.     

One-way flow networks: the role of heterogeneity

I study a one-way flow connections model in which players are heterogeneous with respect to values and the costs of establishing a link. I show that values and costs heterogeneity are equally important in determining the level of connectedness and the architecture of equilibrium networks. I also show that when asymmetries are independent of the potential partner there are distributions of costs and values for which centrality is a distincitive feature of equilibrium networks. This sharply contrasts with the homogeneous case.I thank an anonymous referee for useful comments. The paper has benefited from discussion with Gabriella Conti, Jose Luis Moraga-Gonzalez, Fernando Vega-Redondo and Sanjeev Goyal.     

Evolution of networks—an experimental analysis

It is the main aim of our paper to study network formation in experimental setups in discrete and continuous time. Our design is inspired by the theoretical model on network formation by Bala and Goyal (Econometrica, 68(5): 1181–1229, 2000) as well as the experiments by Callander and Plott (J. Public Econ., 89: 1469–1495, 2005) and Falk and Kosfeld (IEW Working Paper, University of Zürich, Zürich, Switzerland, No. 146, 2003). In particular, we analyze the role of star-shaped networks which are strict Nash-equilibria of the corresponding network formation game. Our experimental results show that strict Nash networks prove to be a good indicator for predicting network formation, particularly in continuous time. In explaining our results, it turns out that, among others, the complexity in coordinating on stars, the inequity aversion against unequal payoff distribution in the network, and the groups’ degrees of activity are the most important determinants for the formation of strict Nash networks.      

Existence of Nash networks in one-way flow models

This paper addresses the existence of Nash equilibria in one-way flow models in a number of different settings. In these models players form costly links with other players and obtain resources from them through the directed path connecting them. We find that heterogeneity in the costs of establishing links plays a crucial role for the existence of Nash networks. The paper also provides conditions for the existence of Nash networks in models where costs and values of links are heterogeneous. We would like to thank an anonymous referee for useful suggestions. We would also like to thank Hans Haller and participants at the AEA Meetings 2007 for helpful comments. Sudipta Sarangi acknowledges the support of NSF grant HSD-0527315 and the hospitality of CREUSET, Jean Monnet University.     

Stochastic stability and time-dependent mutations

This paper considers stochastic stability analysis in evolutionary models with time-dependent mutations. It takes a class of time-homogeneous Markov models where the transition probabilities are approximately polynomial functions of the mutation parameter and allows the mutation parameter to decline to zero over time. The main result shows that as long as the mutation parameter converges to zero slowly enough and its variation is finite, the resulting time-inhomogeneous model has a limiting distribution regardless of the details of the mutation process. Moreover, a bound on the required rate of decline is explicitly expressed as a function of the minimum coradius of the limit sets and the transition probabilities within the minimum coradius set.     

Candidate stability and probabilistic voting procedures

Summary. We extend the analysis of Dutta, Jackson and Le Breton (Econometrica, 2001) on strategic candidacy to probabilistic environments. For each agenda and each profile of voters preferences over running candidates, a probabilistic voting procedure selects a lottery on the set of running candidates. Assuming that candidates cannot vote, we show that random dictatorships are the only unanimous probabilistic voting procedures that never provide unilateral incentives for the candidates to withdraw their candidacy at any set of potential candidates. More flexible probabilistic voting procedures can be devised if we restrict our attention to the stability of specific sets of potential candidates.Received: 4 February 2003, Revised: 14 September 2004, JEL Classification Numbers: D71, D72.This is a revised version of a chapter of my Ph.D. Dissertation submitted to the Universitat Autónoma de Barcelona. I am indebted to my supervisor Salvador Barberá for his advice and constant support. I am grateful to Dolors Berga and an anonymous referee for their detailed comments and suggestions. I thank José Alcalde, Walter Bossert, Bhaskar Dutta, Lars Ehlers, Jordi Massó, Diego Moreno, Clara Ponsatí, Yves Sprumont, and William Thomson for many helpful comments and discussions. I thank the hospitality of the C.R.D.E. at the Université de Montréal and the Department of Economics of the University of Warwick where parts of this research were conducted. Financial support through Research Grant 1998FI00022 from Comissionat per Universitats i Recerca, Generalitat de Catalunya, Research Project PB98-870 from the Ministerio de Ciencia y Tecnología, and Fundación Barrié de la Maza is gratefully acknowledged.     

A network experiment in continuous time: The influence of link costs

In recent work on non-cooperative network formation star-shaped networks play an important role. In a particular theoretical model of Bala and Goyal (2000) center-sponsored stars are the only strict Nash networks. In testing this theoretical model, Falk and Kosfeld (2003) do not find experimental evidence that players select the center-sponsored star. Based on a slight modification of Bala and Goyal’s model, we design a network formation experiment in which, depending on link costs, periphery-sponsored stars and the empty network are the only strict Nash networks. We observe that almost all groups not only reach a strict Nash network once but also switch the center player in periphery-sponsored stars several times. The main innovation in our experiment is to use a continuous time framework which we believe to be a more realistic setting to study behavior in network formation situations and which makes coordination on stars much easier than simultaneous strategy adaptation in discrete time. Electronic Supplementary Material Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s10683-006-9125-1. JEL Classification C72 · C92 · D81     

企业网络理论的四大流派综述

在全球化的经济环境中,企业组织结构也随着分工合作范围的扩大而突破了传统界限,这进一步深刻地影响了市场结构。在全球市场的兴起与激烈的竞争环境中,单一组织对于产品的生产越来越多地依赖外部资源,其中由合作伙伴所形成的企业间网络,日益成为组织取得外部资源最有效的方法之一,企业网络的形成是战略管理领域众多学者讨论的问题,研究学者从不同的研究视角对企业网络的形成机制做出了解释。本文在综合国内外学者对企业网络形成机制理论研究的基础上,对企业网络形成机制从资源基础学派、组织学习学派、制度经济学派、经济社会学派四个视角对其进行理论综述,深入探讨了学术界对企业网络本质认识上存在的分歧,尝试对当前企业网络理论在逻辑上做出清晰的梳理。     

Unique stability in simple coalition formation games

We investigate the uniqueness of stable coalition structures in a simple coalition formation model, for which specific coalition formation games, such as the marriage and roommate models, are special cases that are obtained by restricting the coalitions that may form. The main result is a characterization of collections of permissible coalitions which ensure that there is a unique stable coalition structure in the corresponding coalition formation model. In particular, we show that only single-lapping coalition formation models have a unique stable coalition structure for each preference profile, where single-lapping means that two coalitions cannot have more than one member in common, and coalitions do not form cycles. We also give another characterization using a graph representation, explore the implications of our results for matching models, and examine the existence of strategyproof coalition formation rules.     

In search of stars: Network formation among heterogeneous agents

This paper reports results from a laboratory experiment on network formation among heterogeneous agents. The experimental design extends the Bala–Goyal [Bala, V., Goyal, S., 2000. A non-cooperative model of network formation, Econometrica 68, 1131–1230] model of network formation with decay and two-way flow of benefits by introducing agents with lower linking costs or higher benefits to others. Furthermore, agents' types may be common knowledge or private information. In all treatments, the (efficient) equilibrium network has a “star” structure. While equilibrium predictions fail completely with homogeneous agents, star networks frequently occur with heterogeneous agents. Stars are not born but rather develop: with a high-value agent, the network's centrality, stability, and efficiency all increase over time. A structural econometric model based on best response dynamics and other-regarding preferences is used to analyze individual linking behavior. Maximum-likelihood estimates of the underlying structural parameters, obtained by pooling data from several treatments, allow us to explain the main treatment effects.     

Candidate stability and nonbinary social choice

Summary. The requirement that a voting procedure be immune to the strategic withdrawal of a candidate for election can be formalized in different ways. Dutta, Jackson, and Le Breton (Econometrica, 2001) have recently shown that two formalizations of this candidate stability property are incompatible with some other desirable properties of voting procedures. This article shows that Grether and Plott's nonbinary generalization of Arrow's Theorem can be used to provide simple proofs of two of their impossibility theorems. Received: August 15, 2001; revised version: March 11, 2002 RID="*" ID="*" Parts of this article were previously circulated in somewhat different form in a working paper with the same title by the second author. We are grateful to Michel Le Breton and an anonymous referee for their comments. Correspondence to:J.A. Weymark     

A note on cartel stability and endogenous sequencing with tacit collusion

We use the concept of cartel stability defined by d’Aspremont et al. (Can J Econ 16(1):17–25, 1983) to obtain that the sequence of play between the cartel and the fringe affects cartel stability in a quantity-competition setting where firms tacitly collude. We also prove that an endogenous sequence of play between a cartel and a fringe depends on the discount factor. If the discount factor is large enough, the cartel and the fringe simultaneously choose quantities since the stable cartel may contain more firms under simultaneous play than under cartel leadership. This is due to the fact that under simultaneous play cartel firms have incentives to participate in the cartel because otherwise no collusion is possible.      

Free banking and the stability of early joint-stock banking

Proponents of free banking argue that systems adopting theirpolicies will be stable. In this paper, we present evidencesuggesting that, in general, early joint-stock banking systemsdid not adopt free banking, and those that did proved to beunstable. In particular, we demonstrate that those systems imposingregulations were generally stable. We rationalise the successof regulation as a pragmatic solution to the time-inconsistencyproblem arising from the peculiar nature of the banking firm.Notably, we find that the ‘golden age’ of free bankingstability can be attributed to restrictions on the organisationalform of the early banking firm.     

The evolutionary stability of constant consistent conjectures

In the general context of smooth two-player games, this paper shows that there is a close connection between (constant) consistent conjectures in a given game and the evolutionary stability of these conjectures. Evolutionarily stable conjectures are consistent and consistent conjectures are the only interior candidates to be evolutionarily stable. Examples are provided to illustrate the result.     

基于分层的WSN非均匀模糊分簇路由

基于分簇拓扑的无线传感器网络中常出现的"热区"问题,文章提出一种非均匀分簇的无线传感器网络多跳路由协议,基本思路是将网络划分为宽度不等的层来构建非均匀的簇,路由算法按轮运行。结合剩余能量和密集度,利用Mamdani模糊推理进行层内的簇首选择,构建层间路由树让簇首以多跳方式与基站进行通信。仿真结果表明该算法能够有效缓解"热区"问题,延长网络存活时间。     

Conjectural variations and evolutionary stability in finite populations

Recently it has been shown that consistent conjectures are evolutionarily stable. In this note we show that this finding depends on the use of the infinite population ESS (Maynard-Smith, Evolution and the theory of games, Cambridge University Press, Cambridge, UK, 1982). When applying the finite-population ESS (Schaffer, J Theor Biol 132:469–478, 1988) we show that the conjectures surviving in the long run are not consistent.      

Money demand stability: Evidence from Spain

Using several tests for structural stability in regressions with I(1) variables and for the existence of cointegration in models with regime shifts, the empirical evidence on the existence of a structural break in the Spanish long-run demand for broad money (ALP2) is analysed.The results indicate that shifts affecting the demand for ALP2 in recent years have substantially altered its long-run properties. As to the cause of this structural break, emphasis is placed on the role played by the increasing openness of the Spanish financial system to international markets as obstacles to free capital movements have progressively disappeared.This paper represents the views of the author and should not be interpreted as reflecting those of any institution. I am grateful to J. Ayuso, J. J. Dolado, F. Restoy and two anonymous referees for helpful comments. The data may be obtained from the internet, http://wotan.wiwi.hu-berlin.de/oekonometric/engl/data.html. This paper was written while the author was working at the Banco de España.     

Information Sharing within the Networks of Delegated Portfolio Managers: Evidence from Plan Sponsors and Their Subadvisers

The authors study information sharing among delegated portfolio managers through networks connected by investment mandates between plan sponsors and their subadvisers. Specifically, they identify similarity in returns, holdings, and trading between mutual funds operated by subadvisers, and test whether such similarity is stronger when two funds share a mandate network. The authors find evidence consistent with information sharing among these delegated portfolio managers. A mutual fund on average shares more similar returns, holdings, and trading with funds in subadvisory mandate networks than with funds outside the networks. Preliminary evidence suggests that information about both general investment styles and individual firms is transferred within mandate networks.