《国际贸易（第七版）》Chap003

TheClassicalWorldofDavidRicardoandComparativeAdvantageChapter3LearningObjectivesExplaincomparativeadvantageasthebasisoftrade.Identifythedifferencebetweenabsoluteandcomparativeadvantage.Calculategainsfromtradeina2x2model.Illustratecomparativeadvantageusingproductionpossibilityfrontiers.AssumptionsoftheRicardianModelA2-country,2-commodityworldPerfectcompetitionNotransportationcostsFactorsmobileinternally,immobileinternationallyConstantcostsofproductionFixedtechnologyforeachcountryAllresourcesarefullyemployedThe“labortheoryofvalue”holdsNotationLet:ax=labortimetoproduce1XincountryAay=labortimetoproduce1YincountryAbx=labortimetoproduce1XincountryBby=labortimetoproduce1YincountryBComparativeAdvantageDefinedCountryAhasacomparativeadvantageingoodXif:(Px/Py)A<(Px/Py)B

ORifax/ay<

bx/byORifax/bx<

ay/byIfcountryAhasacomparativeadvantageingoodX,

countryBmusthaveacomparativeadvantageingoodY.ComparativeAdvantage:AnExample3-6ComparativeAdvantageSincetheU.S.’sAPRforcornislowerthanMexico’s(1/5<1/2),theU.S.musthaveacomparativeadvantageincorn.SinceMexico’sAPRforblanketsislowerthantheU.S.’s(2<5),Mexicomusthaveacomparativeadvantageinblankets.ComparativeAdvantageandtheTotalGainsfromTradeRicardo’sargumentisthattradewillbemutuallyadvantageousaslongasthetwocountries’autarkypriceratiosaredifferent.Howdoweknowthatthisistrue?ComparativeAdvantageandtheTotalGainsfromTradeTheProductionPossibilitiesFrontier(PPF)isthesetofallcombinationsofgoodsthatacountryiscapableofproducing,givenavailabletechnologyandresources.SupposeinourexampletheU.S.has1000hoursoflaboravailableandMexicohas1800.U.S.ProductionPossibilities1000CornBlankets200500100ASlope:rise/run=-1000/200=-5SlopeofthePPFforthisexample,-5Notice:theslope(inabsolutevalue)istheAPRofthegoodonthehorizontalaxis.Therefore,theslopeistheopportunitycostofthegoodonthehorizontalaxis.Theslopeisalsothemarginalrateoftransformation.Mexico’sProductionPossibilities600CornBlankets300Slope=-2,ortheopportunitycostofblanketsClassicalModel:TheGainsfromTradeSupposethatinautarky,theU.S.isatpointA,producingandconsuming500cornand100blankets.Supposethatinautarky,MexicoisatpointB,producingandconsuming300cornand150blankets.U.S.ProductionPossibilities1000CornBlankets200500100AMexico’sProductionPossibilities600CornBlankets300300150BClassicalModel:TheGainsfromTradeSupposenowthattheU.S.andMexicoagreetotradeatan“exchangerate”of1B=3.33C(or,1C=.3B).IftheU.S.specializesincorn,howmanyunitsofcorncoulditproduce?1000.IfMexicospecializesinblanketmanufacture,howmanyblanketscouldbemade?300.TheGainsfromTrade:U.S.IftheU.S.wantstocontinuetoconsume500C,theywillnowhave500Ctotradeforblankets.Ifthe“exchangerate”is1B=3.33C(or,1C=.3B),howmanyblanketscantheU.S.getinexchangefor500C?150Therefore,theU.S.canconsumeoutsideitsPPF(topointC)bytrading!U.S.ProductionPossibilities1000CornBlankets200500100CA150TheGainsfromTrade:MexicoIfMexicowantstocontinuetoconsume150B,theywillnowhave150Btotradeforcorn.Ifthe“exchangerate”is1B=3.33C(or,1C=.3B),howmuchcorncanMexicogetinexchangefor150B?500Therefore,MexicocanalsomoveoutsideitsPPF(topointD)bytrading!Mexico’sProductionPossibilities600CornBlankets300150B300500DTheGainsfromTradeNote:Ingeneral,theRicardianmodelresultsincompletespecialization.However,intradebetweenasmallandalargecountrythesmallcountrymaynotbeabletoproduceenoughtosatisfythelargecountry;thelargecountrymightthenpartiallyspecialize.TheConsumptionPossibilitiesFrontier(CPF)TheCPFisacollectionofpointsthatrepresentcombinationsofcornandblanketsthatacountrycanconsumeifittrades.U.S.ConsumptionPossibilities1000CornBlankets200500100CA150300CPFTheConsumptionPossibilitiesFrontier(CPF)TheCPF’sslopeisthesameasthetermsoftrade.TheCPFpivotsaroundtheproductionpoint.Iftradeistothebenefitofacountry,theCPFliesoutsidethePPF.Mexico’sConsumptionPossibilities600CornBlankets300150B300500D1000CPFTheLimitstoMutuallyAdvantageousTrade“Exchangerate”mustbeatleastasgreatasMexico’sAPR.“Exchangerate”mustbenogreaterthantheU.S.’sAPR.Bottomline:westilldon’tknowhowthetermsoftradewillbedetermined,buttheymustbebetweenthecountries’APRsiftradeistobemutuallybeneficial.TheCPFand“Small”CountriesThenearerarethetermsoftradetoac