COMPLEXITY IN ECONOMICS.docx
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COMPLEXITY IN ECONOMICS.docx
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COMPLEXITYINECONOMICS
COMPLEXITYINECONOMICS
EditedbyJ.BarkleyRosser,Jr.[bookforthcoming,EdwardElgar,2003]
Introduction
TheEmergenceofComplexityinEconomics
Increasinglyineconomicswhathadbeenconsideredtobeunusualandunacceptablehascometobeconsideredusualandacceptable,ifnotnecessarilydesirable.Whereasithadbeenwidelybelievedthateconomicrealitycouldbereasonablydescribedbysetsofpairsoflinearsupplyanddemandcurvesintersectinginsingleequilibriumpointstowhichmarketseasilyandautomaticallymoved,nowitisunderstoodthatmanymarketsandsituationsdonotbehavesowell.Economicrealityisrifewithnonlinearity,discontinuity,andavarietyofphenomenathatarenotsoeasilypredictedorunderstood.Atthesametimethebroadcoherenceofeconomicsystemsismoreimpressivethaneverinthefaceofsuchphenomena.Theorderoftheeconomyappearstoemergefromthecomplexinteractionsthatconstitutetheevolutionaryprocessoftheeconomy.
Thesephenomenahavecometobelabeledascomplexityineconomics.Evenwhatseemssimpleineconomicsgenerallyarisesfrombehaviornotreflectingrationalexpectations;weliveinaworldthatreflectstheenormousvarietyanddiversityofhumanityintheirknowledge,attitudes,andbehaviors,interactingwitheachotherinanenormousrangeofinstitutionalframeworks.Whatemergesintheaggregatemayhavelittletodowithwhathappensattheindividuallevel.Butthisaggregatecannotbesimplydescribedbysomesetofaggregateequations.Itemergesoutofthesoupoftheindividualandparticularwithallitsmultiforminteractionsandpeculiarities.
Thischangeofperspectivehasbroughtforthavarietyofnewapproachestoanalysis.Previouslyapremiumwasplacedondeductiveformalproofsoftheoremsthatsoughttoderivegeneralsolutionsbroadlyapplicable,aviewthatreacheditsculminationintheFrenchBourbakistschool.Nowweseeagreateremphasisoncomputersimulationsandexperimentalmethodstoinductivelydeterminepossibleoutcomesandrangesofsolutions.Emergentphenomenafromcomplexsystemsarenotusuallydiscoveredbytheoremsbutmorefrequentlybytheuseofincreasinglypowerfulcomputerstoexplorethelimitsandpossibilitiesthatcanarise.Thenewawarenessoftheubiquityofcomplexityistransformingthewaythatwethinkabouteconomics.
WhatisEconomicComplexity?
Theideathatrealityreflectscomplexitydidnotinitiallyariseineconomics.Ithascomefromnumerousdisciplinesofthoughtandhasreverberatedbackandforthacrossthem,frommathematicsandcomputersciencetophysicsandbiologytothesocialsciencesandbackandforth.Thatdifferentdisciplineshavecometoseeitasmeaningsomethingsomewhatdifferentfromwhatotheronesdoisnotsurprising.Indeed,thephysicist,SethMiller,hasgatheredatleast45differentdefinitionsof“complexity.”Manyofthesearenotappropriateforeconomics,oronlybarelysoforspecialoccasionsorcircumstances.Computerscienceistheoriginofmanyofthese,andarguablymanyoftheseareamongthemorerigorousofsuchdefinitions,suchasthelengthofanalgorithmforsolvingaspecificproblem.SuchideashadimportantinfluenceoneconomicthinkingthroughsuchfiguresasHerbertSimon,animportantfigureinthedevelopmentofartificialintelligenceincomputerscienceaswellasaNobelPrizewinnerineconomicsforhisconceptualizationofboundedrationality.Butthisisnotwhatmosteconomiststhinkofwhentheythinkofcomplexeconomicdynamics,althoughrealityofcomplexityineconomicshascomefullcircletoSimoninimplyingtheinevitabilityofboundedrationality.Economiccomplexityisnotsimplyamatterofthingsbeing“complicated,”althoughsomehavevieweditthisway,andcertainlyeconomicrealityisboth“complicated”aswellascomplexinthesensethathasincreasinglycometobeacceptedasmostrelevantforeconomics.
Attheriskofoversimplifyingcomplexity,weshallfollowRichardDay(1994)indefiningcomplexityineconomicsintermsofdynamicoutcomes.Aneconomicsystemisdynamicallycomplexifitsdeterministicendogenousprocessesdonotleaditasymptoticallytoafixedpoint,alimitcycle,oranexplosion.Somemightarguethatendogenouslimitcyclesalsoconstitutecomplexity,butweshallviewthemasmerelynearlycomplex.Wenotethatallsystemsthatfitthisdefinitionhavesomedegreeofnonlinearitywithinthem,howeverlimitedorarbitrary.Atthesametimetherearenonlinearsystemsthatarenotcomplex,suchasastandardexponentialgrowthmodel.
Nowweobservethatthisisa“broadtent”definitionofcomplexitythatincludessystemsthatsomewouldargueshouldnotbeincluded.Thereisa“narrowtent”viewofeconomiccomplexity,butitlacksasimpleorcleardefinition.Itcanonlybecharacterizedbyfittingwithasetofcharacteristics.Arthur,Durlauf,andLane(1997)providesuchalistofcharacteristics.Theyinclude1)dispersedinteractionamongheterogeneousagentsactinglocallyoneachotherinsomespace;2)noglobalcontrollerthatcanexploitallopportunitiesorinteractionsintheeconomyeventhoughtheremightbesomeweakglobalinteractions;3)cross-cuttinghierarchicalorganizationwithmanytangledinteractions;4)continualadaptationbylearningandevolvingagents;5)perpetualnoveltyasnewmarkets,technologies,behaviors,andinstitutionscreatenewnichesintheecologyofthesystem,and6)out-of-equilibriumdynamicswitheitherzeroormanyequilibriaexistingandthesystemunlikelytobenearaglobaloptimum.
Howdothesetwoapparentlycompetingperspectivesrelatetoeachotherandhowarewegoingtodealwiththeminthiswork?
Thesecondwillgenerallybeasubsetofthefirst(althoughtherearecertainlysystemsthatcouldfulfillallsixofthesecharacteristicsandyetviolatethefirstdefinition).Moreaccuratelyitcanbearguedthatthesecondisthehistoricaloutcomeofthefirst.InhisessayreproducedinSectionI,JohnHorgan(1995)criticizestheconceptof“complexity”moregenerally,notjustineconomics,asjustthelatestinastringoffads,“thefourC’s.”InhisviewthesefourC’sarecybernetics,catastrophe,chaos,andcomplexity.Thisreflectstheapproximateorderoftheirappearanceasbroad,transdisciplinaryfads,withcyberneticshotinthe1960s,catastrophetheoryhotinthe1970s,chaostheoryhotinthe1980s,andcomplexitycominginduringthe1990s.InHorgan’svieweachofthesewasoverhyped,wasasortofintellectualbubblethatblewupandthencrashed.Forhimcomplexityisjustthelatestoftheseandwillcrashalso.
TheviewofthisintroductionistotakeHorgan’sargumentseriouslybuttoturnitonitshead.First,heiscorrecttoidentifyintellectuallinkagesbetweentheseintellectualmovements.Theyallareapartofcomplexityinour“broadtent”sense.Notonlythat,buttheyhavetosomedegreearisenoutofeachother,eventhougheachhasspecificsharpdifferencesfromtheothers.Thisisevenreflectedinthatcertainindividualshaveplayedrolesinvariousofthesestages,withafewevenarguablyhavingbeeninvolvedinallfour.Thereisanintellectualunityto“broadtent”complexity.
Second,heiswrongtohaveviewedthemashavingsimplydisappearedwhenthey“crashed”aftertheiradmittedlyrespectiveoverhypings(althoughitisnotclearthatthelast,“narrowtent”complexity,hasactually“crashed,”despitevariousdoubtsandcaveatshavingbeenraisedaboutit).Cyberneticslivesoninthenewercomplexitythroughtheuseofsimulationandtheideathat“counterintuitive”resultscanarisefromsimulatingsystemsofnonlineardifferentialequations.Catastrophetheory,perhapsthemostcriticizedand“academicallyunacceptable”ofthefour,persistsinthewidespreadperceptionoftherealityofprofounddiscontinuity,whetheritisthecrashofastockmarketoracurrency,orthecollapseofanecologic-economicsystem.Thenewercomplexitytheoryofdispersedagentshasdiscovereditsownwaysofgeneratingthisoutcomeoftheoldertheory.Thesituationwithchaostheoryismorecomplicatedasitsprogenitorsandpractitionersareevenmorecloselylinkedtothenewerviews.ThisfactisrecognizedbyHorganinhislabelofchaoplexology,whichmaybeanon-category,butwhoseveryexpressiongivescredencetotheideaoftheunityofthestreamofideasthathavebeenbuildingoverseveraldecadestoreachacriticalintellectualmassthatisnowmoreprofoundlyalteringtheviewsofeconomistsmorewidely.
Ourapproachwillbetopresentpapersthattendtoemphasizethemorerecentviewpoint,whichisclearlywhatisgenerallydrivingmorerecentresearch.However,weshallalsoincludecertainpapersthatrepresenttheearlierperspectivesofthebroaderdefinitionofeconomiccomplexitythatwehavepresented.Thiswillallowforbothhistoricalaccuracyandalsotoshowtheessentialunityoftheseapproachesasmanypaperswillmixvariousofthesesupposedlydistinctviewpoints.Howeverthebookwillbeorganizedbyareasofeconomics.Thuswithineachareatherewillbepapersofvariousoftheperspectives,althoughgenerallywithagreateremphasisonthemorerecentviewofwhateconomiccomplexityis.WenotehoweverthatweshallnotincludeanypapersthathavealreadyappearedinthevolumeonchaostheoryeditedbyDechert(1996),althoughsomeofthosewouldhavebeencandidatesforthisvolume.
Weshallnowproceedwithasummaryofthepaperspresentedintheirtencategories.
PhilosophicalandMethodologicalOverviews
Thefirstpaperdatesfrom1962,longbeforethecurrentdiscussionsofthemeaningornatureofcomplexityineconomics.Indeeditisnotex
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