This page intentionally left blank Economicsandthetheoryofgames This textbook offers a systematic, self-contained account of the main contribu- tions of modern game theory and its applications to economics. Starting with a detaileddescriptionofhowtomodelstrategicsituations,thediscussionproceeds bystudyingbasicsolutionconcepts,theirmainrefinements,gamesplayedunder incompleteinformation,andrepeatedgames.Foreachofthesetheoreticaldevel- opments,thereisacompanionsetofapplicationsthatcoverthemostrepresentative instancesofgame-theoreticanalysisineconomics,e.g.,oligopolisticcompetition, public goods, coordination failures, bargaining, insurance markets, implementa- tion theory, signaling, and auctions. The theory and applications covered in the first part of the book fall under the so-called classical approach to game theory, which is founded on the paradigm of players’ unlimited rationality. The second partshiftstowardtopicsthatnolongerabidebythatparadigm.Thisleadstothe studyofimportanttopicssuchastheinterplaybetweenevolutionandrationality, thebehavioraldynamicsinducedbysociallearning,andhowplayersmighttackle theproblemofmultipleequilibria. FernandoVega-RedondoiscurrentlyProfessorattheUniversidaddeAlicanteand theUniversitatPompeuFabra.Hisrecentresearchhasfocusedonbothgamethe- oryandlearningandotherinterdisciplinaryfieldssuchasevolutionandComplex networks.Hispapershavebeenpublishedinawidearrayofinfluentialjournals including Econometrica, Journal of Economic Theory, International Economic Review,GamesandEconomicBehavior,EconomicTheory,JournalofTheoretical Biology, and Physical Review Letters. Professor Vega-Redondo is author of the book Evolution, Games and Economic Behavior and the Spanish-language text- book Econom´ıa y Juegos: Teor´ıa y Aplicaciones. He has been a visiting scholar at the Indian Statistical Institute; the Institute for Advanced Studies in Vienna; theHebrewUniversityofJerusalem;andtheUniversitiesofHarvard,California– SanDiego,andBoston.Heisco-editorofSpanishEconomicReviewandmember oftheEditorialBoardofLectureNotesinEconomicsandMathematicalSystems. ProfessorVega-RedondoreceivedhisPh.D.fromtheUniversityofMinnesota. Economics and the theory of games FERNANDO VEGA-REDONDO UniversidaddeAlicanteandUniversitat PompeuFabra,Spain ToOlalla, whohappilyenteredthegameasIwascompletingthelast stagesofthisbook Cambridge, New York, Melbourne, Madrid, Cape Town, Singapore, São Paulo Cambridge University Press The Edinburgh Building, Cambridge , United Kingdom Published in the United States of America by Cambridge University Press, New York www.cambridge.org Information on this title: www.cambridge.org/9780521772518 © Fernando Vega-Redondo 2003 This book is in copyright. Subject to statutory exception and to the provision of relevant collective licensing agreements, no reproduction of any part may take place without the written permission of Cambridge University Press. First published in print format 2003 - ---- eBook (NetLibrary) - --- eBook (NetLibrary) - ---- hardback - --- hardback - ---- paperback - --- paperback Cambridge University Press has no responsibility for the persistence or accuracy of s for external or third-party internet websites referred to in this book, and does not guarantee that any content on such websites is, or will remain, accurate or appropriate. Contents Preface pagexi 1 Theoreticalframework 1 1.1 Introductionandexamples 1 1.2 Representationofagameinextensiveform 4 1.3 Representationofagameinstrategicform 12 1.4 Mixedextensionofagame 16 Supplementarymaterial 18 1.5 Mixedandbehavioralstrategies 18 1.6 Representationofagameincoalitionalform 23 Summary 26 Exercises 26 2 Strategic-formanalysis:theory 30 2.1 Dominanceanditerativedominance 30 2.2 Nashequilibrium 35 2.3 Zero-sumbilateralgames 45 Supplementarymaterial 50 2.4 Nashequilibrium:formalexistenceresults 50 2.5 Strongandcoalition-proofequilibria 53 2.6 Correlatedequilibrium 56 2.7 Rationalizability 61 Summary 68 Exercises 69 3 Strategic-formanalysis:applications 72 3.1 Oligopoly(I):staticmodels 72 3.2 Mechanismdesign(I):efficientallocationofpublicgoods 83 3.3 Mechanismdesign(II):Nashimplementation 90 3.4 Markets(I):macroeconomiccoordinationfailures 99 Summary 104 Exercises 105 4 RefinementsofNashequilibrium:theory 110 4.1 Introduction 110 4.2 Refinementsexcluding“incrediblethreats”:examples 110 4.3 Subgame-perfectequilibrium 115 4.4 WeakperfectBayesianequilibrium 117 Supplementarymaterial 120 vii viii Contents 4.5 Refinementsexcluding“untenablebeliefs”:examples 120 4.6 Sequentialequilibrium 128 4.7 Perfectandproperequilibria 131 4.8 Strategic-formrefinements 135 Summary 143 Exercises 144 5 RefinementsofNashequilibrium:applications 151 5.1 Oligopoly(II):sequentialmoves 151 5.2 Markets(II):decentralizedpriceformation 159 5.3 Oligopoly(III):differentiatedproducts 171 5.4 Mechanismdesign(III):efficientallocationofanindivisibleobject 176 Summary 182 Exercises 184 6 Incompleteinformation:theory 188 6.1 Introductionandexamples 188 6.2 Bayesiangames 191 6.3 Bayes-Nashequilibrium 196 6.4 Signalinggames 204 Supplementarymaterial 217 6.5 Mixedstrategies,revisited:apurificationapproach 217 6.6 Forwardinduction 221 Summary 225 Exercises 226 7 Incompleteinformation:applications 231 7.1 Markets(III):signalinginthelabormarket 231 7.2 Markets(IV):insurancemarketsandadverseselection 244 7.3 Mechanismdesign(IV):one-sidedauctions 254 7.4 Mechanismdesign(V):buyer–sellertrade 267 Summary 275 Exercises 276 8 Repeatedinteraction:theory 281 8.1 Introductionandexamples 281 8.2 Repeatedgames:basictheoreticalframework 283 8.3 Folktheorems:Nashequilibrium 286 8.4 Reputationand“irrationality”:informaldiscussion 294 Supplementarymaterial 300 8.5 Folktheorems:subgame-perfectequilibrium 300 8.6 Reputationand“irrationality”:formalanalysis 311 Summary 319 Exercises 321 9 Repeatedinteraction:applications 324 9.1 Oligopoly(IV):intertemporalcollusioninaCournotscenario 324 9.2 Oligopoly(V):intertemporalcollusioninaBertrandscenario 334 9.3 Markets(V):efficiencywagesandunemployment 341 Summary 351 Exercises 352
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