Model of International Trade.ppt

ModelofInternationalTrade TheoryandPolicy RicardianModelReviewtheAssumptions Oneinput Labor L Twooutputs TwocountriesCostsareconstantandtherearenoeconomiesofscale Factorsofproductionareperfectlymobile Goodsareidentical Perfectknowledge Notransportcosts Notariffsorothertradebarriers 1RicardianModel 1 生产状况 1 生产函数 FunctionofProduction Yi 1 ai Lii 1 2其中ai表示投入产出系数 2 成本函数 FunctionofCost Pi aiw工资率w决定价格水平 技术决定相对价格 1RicardianModel 2 一般均衡条件a1Y1 a2Y2 LQ P1Y1 P2Y2 wLU Q D1 UZ1 Y1 D1Z2 Y2 D2 1RicardianModel 3 问题求解该问题可分两个步骤求解 第一个步骤 在劳动市场约束的条件下 求收入的最大化 第二个步骤 决定需求和贸易流量 步骤1 收入最大化maxQ P1Y1 P2Y2 wLs ta1Y1 a2Y2L这是一个线性规划问题 存在三种可能 P1 P2a1 a2可行解为Y2 0 Y1 a1LP1 P2 a1 a2可行解为沿a1Y1 a2Y2 L直线上的Y1 Y2的任意组合 1RicardianModel 4 比较优势和贸易方式在封闭经济条件下 比较优势由技术决定 P1 P2 a1 a2如果P1 P2 P 1 P 2 本国应出口Y1 进口Y2 这里P 1 P 2是世界相对产品价格 贸易方式依赖于在相对平均成本上的差别而不是绝对成本 通常P1 P2P 1 P 2 因此 一个国家应从事专门化生产 根据比较优势从事专业化所得的收益 将通过处于封闭和自由贸易条件之间的世界价格和收入的差异来度量 本国与外国的相对成本的差别越大 则根据比较优势 从专业化中获得的收益越多 1RicardianModel 5 贸易条件设P1 P2是世界相对价格 在一个由本国和外国组成的世界 如果 说明本国是大国 外国是小国 本国可生产两种产品 而外国则专门生产产品2 如果 说明本国和外国都不能主宰世界市场 两国应专业化生产 本国专门生产产品1 外国专门生产产品2 如果 说明外国是大国 本国是小国 外国可生产两种产品 而本国则专门生产产品1 1RicardianModel ConclusionTheprincipleofcomparativeadvantageisstilleffectiveundertheincreasingopportunitycost However purespecializationisimpossible 1RicardianModel 放宽李嘉图模型的某些假设 并不会对比较优势原则造成实质性的影响 只是增加了国际贸易的交易成本 形成了不完全分工 减少了国际贸易的数量 但是 产品同质性和不存在规模经济等假设的放宽 则是部门内贸易理论和规模经济贸易理论等现代贸易理论产生的基础 1RicardianModel IncreasingTransactionCosts Whatistransactioncosts expenseofsearchingforatradingpartner specifyingtheproduct s tobetraded negotiatingthepriceandcontract andtheexpostcosts Whofindthe transactioncosts ReasonsoftransactioncostsespeciallyinITImperfectInformation Knowledge TransportCostTradeBarrierPoliticalRisk 1RicardianModel ImperfectSpecialization IncreasingOpportunityCostTransactionCostsTheSizeofTraderTheexistenceofmorethanonefactorofproductionreducethetendencytowardspecialization Talkaboutitlater C A trademodels Differenttrademodelsfocusondifferent sourcesofcomparativeadvantage i e differentreasonsforwhyrelativecostswouldvaryacrosscountries Typicallyeachtrademodelfocusesononlyonecause i e Explore why differentcostsofproduction 2 WhyDoWeTrade 2 2ModernTradeTheory Heckscher OhlinModel 14 TheBasicAssumptionsoftheHeckscher OhlinModel 1 Numberofcountries factors andcommoditiesarealltwo oftenreferredtoasthe2x2x2model 2 Technologyisthesameinbothcountries3 Constantreturnstoscale4 Strongfactorintensity5 Incompletespecialization 2 WhyDoWeTrade 2 2ModernTradeTheory Heckscher OhlinModel 15 TheBasicAssumptionsoftheHeckscher OhlinModelcontinued 6 Perfectcompetition7 Factorsareperfectlymobilewithineachcountrybutperfectlyimmobilebetweencountries8 Tastesarelargelysimilarbetweencountries9 Freetrade10 Transportationcostsarezero H Otheory Heckscher Ohlin Samuelson model Themostimportanttradetheory itisthebenchmark givesemphasisto relative factorendowments Morethan1factorofproduction non trivialchoiceofproductiontechnique choiceaffectedbyfactorprices andthusbytrade AlltechniquesCRStechniques Technologicalknowledgeuniversal thesetofavailableandknowntechniquesthesameeverywhere HOS model 2x2x2 model 2countries 2goods 2factorsofproduction Factorsofproduction capitalandlabour orunskilledandskilledlabouror fullymobilebetweensectorsbutnotmobileinternationally Crucialassumption Sectorsdifferintermsofthefactorintensityofproductiontechniques e g oneofthesectorsismorecapitalintensivethantheother 2Heckscher OhlinModel 赫克歇尔 俄林理论是根据相对要素供给解释比较优势 在这个模型当中 存在两种要素 劳动和资本 而且均可流动 因此这个模型被认为是国际贸易的长期模型 1生产状况1 生产函数Yi 1 ai Lii 1 2其中ai表示投入产出系数2 成本函数Pi aiw工资率w决定价格水平 技术决定相对价格 成本函数 技术 2Heckscher OhlinModel TheExplanationofInternationalTrade Differencesacrosscountriesinrelativeabundanceoffactorsofproduction Assumptions IdenticalTechnologiesIdenticalDemandPatterns假设商品1比商品2更具有劳动密集性 在自由贸易下考虑通过出口商品1 进口商品2来发展经济 2Heckscher OhlinModel 一般均衡模型如下 2Heckscher OhlinModel Stolper Samuelson定理Rybczynski定理 2Heckscher OhlinModel TheHeckscher OhlinProposition 2 dualtoProposition 1 Freetradecausesanincreaseinthefactorpriceofthefactorofproductionwhichisusedintensivelyintheexportindustryandafallinthefactorpriceusedintensivelyintheimportcompetingindustry TheHeckscher OhlinProposition 1 Anycountrywillexportthegoodwhichmakesintensiveuseinitsproductionofrelativeabundantfactorsupply 3TheRicardo VinerModel Summary tradewithproductionendowmentdifferencesrelativefactorpriceeffectseffectofchangesinendowmentsimplicationsofbeingsector specific 3TheRicardo VinerModel Assumptions twofixedfactorsofproductiononemobilefactortwocommoditiesX1andX2linearhomotheticproductionfunctionsdifferencesinendowments TheRicardo VinerModelAlgebra Capitalissectorspecific andlabourismobilebetweensectors Technologiesarelinearhomothetic TheRicardo VinerModel TheRicardo VinerModelInpercentchanges VMPL1 VMPL2 w L1 L2 TheRicardo VinerModellaboursupplyincrease w0 w VMPL1 VMPL2 w L1 L2 TheRicardo VinerModelwithanon tradablessector w0 w S D O1 O2 L1 K11 K21 TheFPEsetintheRicardo VinerModel O1 O2 L1 K11 K21 TheFPEsetintheRicardo VinerModelifK1isinternationallymobile 3特定要素模型的一般均衡分析 Marketequilibruim 3Sector specificfactormodel 假设有两种要素 劳动和资本 劳动是可移动 而资本是固定要素 1 生产Production生产函数 技术 简单地 假设柯布 道格拉斯生产函数CD技术为 i 1 2 短期利润最大化表明 i 1 2 假定和 这两个方程决定这两种要素的需求 在此 假设劳动市场有效率 因为劳动者可以在没有较大成本的条件下在两个部门间自由移动 在这样决定的劳动需求下 充分就业条件表明 这两个利润率可以如下计算 i 1 2 3Sector specificfactormodel 2 一般均衡 3Sector specificfactormodel 3Sector specificfactormodel Whiletheanalyticsofthemodelwereworkedoutinthe1960sbyRonJonesandPaulSamuelson theideasbehinditcanbefoundinthewritingsofJacobVinerintheearlierpartofthecentury andeveninRicardo swritings butRicardousedthemodeltostudyincomedistributionandgrowth nottrade HenceitissometimescalledtheRicardo Viner Jones Samuelsonmodel Again themodelhasthevirtueofparsimony makingthesimplestassumptionstostudyissuesathand andlookingatissuesinageneralequilibriumframework Sector specificfactormodel Sector specificfactormodel 3Sector specificfactormodel Assumeperfectcompetitioninfactormarketsandgoodsmarkets 3Sector specificfactormodel 2 Equilibrium 3Sector specificfactormodel 3Sector specificfactormodel 3Sector specificfactormodel 3Sector specificfactormodel 6 ADualFormulation 4中间投入和非贸易部门模型 1 中间投入 中间投入又称中间产品 有些产品作为中间产品可能只参与最终产品的生产 有些产品既是中间产品也还作为最终产品 在这里主要讨论第一种情况 假设进口的中间投入 M 可以被用来生产两种产品 4含中间投入的一般均衡模型 4中间投入和非贸易部门模型 2 非贸易部门模型 Nontradedsector 在经济实践中 有相当部分的产品不参加贸易 因此必须引入非贸易产品部门和非贸易品的价格 假设商品3为非贸易品 2 包括非贸易品在内的完整模型l三个价格 5SelectedPost Heckscher OhlinTradeModels Today sLecture1 EconomiesofScale the Krugmanmodel 2 Domesticmonopolies3 ImitationLagandTheProductCycleModel4 TheLinderModel5 GravityModels6 GeographyandTrade 1 KrugmanModel Assumptions1 Internaleconomiesofscale2 Monopolisticcompetition non homogeneousgoods 3 Onefactorofproduction labour 4 Identicalpreferences5 Largenumberofgoodsproducedwiththesametechnology6 Fullemployment 2 KrugmanModel Keyassumption1 EconomiesofScale External costperunitdependsonthesizeoftheindustry notthefirm SiliconValley Hollywood Internal costperunitdependsonthesizeofthefirm notindustry Nokia Phillips GE Doublingtheinputsmorethandoublestheoutput increasinginternaleconomiesofscale 3 KrugmanModel Keyassumption2 MonopolisticCompetition Eachfirmproducesadifferentbrandofthegood goodsthatarenotexactlythesame butthataresubstitutesforoneanother Eachfirmtakespricesofrivalsasgiven nostrategicpricing Eachfirmbehavesasifitwereamonopolist However weassumeeasyentryandexit zero profitsinthelongrunoaslongas averagecost price morefirmsenterthemarket 3 KrugmanModelIntroducingTradetotheMonopolisticCompetitionModel Tradeincreasesmarketsize firmsexploitmoreofthereturnstoscale averagecostdecreases pricedecreases numberoffirmsincreases i e alargervarietyofproductsisavailableforsmallerprice everybodyarebetteroffevenifthecountriesareidentical Intra andInter industryTrade Inter industrytrade countriesexportgoodsofoneproductcategoryandimportsgoodsofotherproductcategoryasintheRicardianaswellasintheHeckscher Ohlinmodele g Finlandexportscapital intensiveandimportslabourintensivegoods Intra industrytrade countriesexportandimportproductsofthesameproductscategoryasintheKrugmanmodele g theU S exportsandimportscarsconstitutesabout oftheworldtrade IntroducingTradetotheMonopolisticCompetitionModel SupposethecostsofafirmtaketheformC F cxQ 1 Thefixedcostgivesrisetoeconomiesofscale becausethelargerthefirm soutput thelessisfixedcostperunitThefirm saveragecost totalcostdividedbyoutput isAC C Q F Q c 2 Thefirm smarginalcost amountitcoststhefirmtoproduceoneextraunit isc where Qisthefirm ssalesSisthetotalsalesoftheindustrynisthenumberoffirmsintheindustrybisaconstanttermrepresentingtheresponsivenessofafirm ssalestoitspricePisthepricechargedbythefirmitself Assumeallfirmsinthisindustryaresymmetric i e identicaldemandandcostfunctionsforallfirmsThemethodfordeterminingthenumberoffirmsandtheaveragepricechargedinvolvesthreesteps Toderivearelationshipbetweenthenumberoffirmsandtheaveragecostofatypicalfirm CCcurve Toderivearelationshipbetweenthenumberoffirmsandthepriceeachfirmcharges PPcurve Toderivetheequilibriumnumberoffirmsandtheaveragepricethatfirmscharge intersectionbetweenCCandPP MarketEquilibrium Howdotheaveragecostsdependonthenumberoffirmsintheindustry Weconcludethataveragecostdependsonthesizeofthemarketandthenumberoffirmsintheindustry AC F Q c nxF S c 4 ThemorefirmsthereareintheindustrythehigheristheaveragecostasshownbytheCCcurveinFigure3below ThenumberoffirmsandthepriceThepricethetypicalfirmchargesdependsonthenumberoffirmsintheindustryThemorefirms themorecompetition andhencethelowerthepriceInthemonopolisticcompetitionmodelfirmsareassumedtotakeeachothers pricesasgiven TheTheoryofImperfectCompetition Profit maximizingfirmssetmarginalrevenueequaltotheirmarginalcost cThisgeneratesanegativerelationshipbetweenthepriceandthenumberoffirmsinthemarketwhichisthePPcurve P c 1 bxn 6 Themorefirmsthereareintheindustry thelowerthepriceeachfirmwillcharge TheTheoryofImperfectCompetition AC F Q c nxF S cNumericalExample Carsproducedbyamonopolisticallycompetitiveindustryb 1 30 000F 750 000 000c 5000Twocountries HomeandForeign withthesamecostsofautomobileproductionAnnualsalesofautomobilesare900 000atHomeand1 6millionatForeign MonopolisticCompetitionandTrade ExplainingTradePatterns Inter industrytradereflectsthecomparativeadvantagethepatternoftradeisdeterminedbyrelativefactorendowments technologicaldifferences Intra industrytradereflectseconomiesofscalethepatternoftradeisunpredictableTherelativeimportanceofthetwokindsoftradedependonhowsimilarthecountriesare OtherExplanationsofIntra IndustryTrade Transportcostsinlargecountries e g abuyerinMainebuystheCanadianratherthantheCalifornianproduct Dynamiceconomiesofscale productdifferentiation learning by doing ProblemswithstatisticsAggregation thecategoriesaretoowide e g beveragesandtobacco Differentqualityofgoodsinsideaproductcategory Domesticmonopolies Domesticmonopolyenteringworldmarkets Singlemonopoly pricediscrimination Twodomesticmonopoliesenteringworldmarkets reciprocaldumpingmodel DomesticMonopolyEnteringWorldMarkets Singleworldsupplier PriceDiscrimination Dumping Oneofthemostheated activedebatesontradeconcerns dumping Roughly thismeansthatdomesticproducerscomplainthatforeigncompetitorsaresellingatunfairlylowpricesandhencethereshouldbe antidumpingmeasures tariffs quotas Thereare atleast twodefinitionswhat dumping means Economicsdefinition Pricediscriminationinthecontextofinternationaltrade afirmischarginglower higherpriceforitsexports Pragmatic lawyers definition thepriceislessthanproductioncost Thiscouldbeanindicatorofpredatorypricingwheretheaimistodrivethedomesticcompetitoroutofthemarketandafterwardstheforeignfirmwoulduseitsmonopolypowerandincreaseprices andhencehurttheconsumers ReciprocalDumpingModel Twocountries twofirmsproducingidenticalgoods transportationcosts First botharedomesticmonopolies Then bothentereachothersmarkets duopoly twofirmstakingintoaccountthebehaviourofeachotherwhenchoosingpricesandquantities Inthe Nash equilibriumpriceandoutputaredeterminedineachmarketforeachfirm gettingtheresultrequiressomeknowledgeofgame theory sowewillnotderiveithere Thepointisthatthepriceisdifferentinhomeandforeignmarkets hence dumping ImitationLag Assumethatittakestimefornewtechnologytospread Imitationlag thetimebetweenproduct sintroductionincountry1andappearanceofaversionofthatproductproducedincountry2 Demandlag timebetweenproductsappearanceincountry1anditsacceptanceincountry2 Netlag imitation demandlag Tradefocusesonnewproducts ImitationLag Figure TradePatternsandProductCycleTheory DynamicComparativeAdvantage Dynamiccomparativeadvantage sourceofexportsshiftthroughoutthelifecycleofthegood e g electronics cars Resultingfromeconomiesofscale factormobilityandinnovation KempModel Kempmodel implicationsofincreasingreturnstoscaleTwogoodsandtwocountries goodsXandY bothgoodshaveincreasingreturnstoscaleinproductioneconomiesofscalearesuchthattheppfisconvextotheorigin economiesofscaledonotalwaysimplyaconvexppf economiesofscaleareEXTERNALtothefirm andpertaintotheindustry Kemp continued therearethreepossibleequilibria1 onlygoodXisproduced2 onlygoodYisproduced3 bothgoodsareproduced andppfistangenttoindifferencecurve NOTASTABLEequilibrium Ifeconomyhappenstobeatequilibrium3 andcountrystartstotrade itwillmovetoeither1or2 dependingonthetermsoftrade patternoftrademaydependonhistoricalaccident sinceforsomeTOTproductionofeithergoodispreferabletoproductionofbothgoods Kemp continued Inthediagram AtTOT1onlyXisproducedAtTOT2onlyYisproduced AtTOT3eitheronlyX oronlyYorsomemixtureisproduced whoknows note themiddleequilibriumisunstable andcanonlyoccurbycoincidenceWitheconomiesofscaleiftwocountrieshavesameppfandsametastesandthereforesamePX PYtheycanstillgainfromtrade Kemp sModel IftheopeningofthecountrytotradeleadstoaTOTlinesteeperthanTOT1 thecountrywillcompletelyspecialiseinXbyproducingatN IftheTOTlineisflatterthanTOT2 thecountrywillcompletelyspecialiseinXbyproducingatN IftheTOTlinefallsinbetweenTOT1andTOT2 itisunclearwherethiscountryproduces However eveninthiscase acompletespecialisationwillgiveahigherutilitybytrade Atwo goodworldwherebothindustriesexperienceEOS PPFisconvextotheorigin Kemp模型 外部规模经济的贸易理论 1 凸向原点的PPF假定 两种商品生产中都存在规模经济 外部规模经济 行业规模扩大导致单个企业成本递减 规模经济导致PPF凸向原点 在凸向原点的PPF上 经济均衡点不稳定 2 专业化方式 开放贸易后 专业化方式取决于一国所面临的特定的贸易条件 贸易条件 TOT1 完全专业化生产X N点 按该贸易条件出口 贸易条件 TOT2 完全专业化生产Y M点 按该贸易条件出口 TOT1 贸易条件 TOT2 贸易方式不能确定 三种可能 a 完全专业化生产X 按照TOT3进行贸易 有正贸易收益 b 完全专业化生产Y 按照TOT3进行贸易 有正贸易收益 c 在F点上同时生产两种商品 按照TOT3进行贸易 不稳定点 在PPF内部消费 贸易方式 规模经济导致了贸易的多种可能性 1 一国在M点生产 另一国在N点生产 两国都将从贸易中获利 2 一国在F点生产 另一国在M或N点生产生产条件和需求偏好都相同的两国都能从贸易中获利 贸易模式的确定可能是偶然的 LinderTheory LinderTheory demandsideoftrade H Ocentresonexpectedtradepatternswhencountrieshavedifferentcapacitiesforproduction butsimilartastesH Odoesexplaintradepatternstosomeextent butinitspurestform H Owouldleadtotheconclusionthatdevelopedcountriesaremorelikelytotradewithdevelopingcountries whohaveverydifferentendowments ratherthanwitheachother LinderTheorycontinued Assumptionsconsumertastesdependonpercapitaincomelevel percapitameansperhead orperperson productionathomedependsontastestradeisaby productofthehomemarket sproductionandconsumptionpatternSo inacountrywithsomeinequality thegoodsdemandedwillreflectthetastesofpeopleatvaryinglevelsofincome andthegoodsproducedwilldependonthesizeofthemarketdemand LinderTheory Example Letgoodsproduced andconsumed bycountryIbeorderedaccordingtoquality A B C D E Alowest EhighestLetcountryIIhaveincomedistributionthatfitsdemandforgoodsC D E FandGThen tradewouldoccuringoodsC D E wherebothcountrieshaveademandforthegoodwewouldthereforeexpectmosttradetobeintra industrytrade countriesshouldbothimportandexportthesamegoods LinderTheory Example LetcountryIIIhaveincomesuchthatitproducesgoodsE F G H andICountryIIIwilltradegoodsE F GwithcountryIICountryIIIwilltradeonlygoodEwithcountryITHEREFORE countrieswilltradetogethermore iftheyhavesimilarpercapitaincomes MOSTtradewillbeintra industrytrade andwiththistheory wecannotpredictthepatternoftrade whichcountrywillexportmore lessofwhichgood LinderTheory testsandimplications testsofLindertheoryhaveshownittobeagoodpredictoroftradeProblemitcan tpredictpatterns norvolumes TheLinderModel Demand orientedmodeltoexplaintradeinmanufacturedgoods Preferencesdependonthelevelofincome tastesyielddemandsforproducts demandsleadtoproduction thekindsofgoodsproduceddependonthepercapitaincomelevelofacountry Tradeoccursifthereisoverlappingdemand Tradewillbemoreintensethemoresimilarthecountriesare TheLinderModel Example LetAbethelowestqualityandJthehighestqualitygood Letcountry1bethepoorestandcountry3therichest seegraph Thencountry1consumesandproducesgoodsA D country2goodsC Fandcountry3goodE J Countries1and2maytradegoodsC D countries2and3maytradegoodsE Fandcountries1and3havenobasisfortrade TheLinderModel Example 如图所示 aa bb 和cc 分别是发展中国家A 中等发达国家B 发达国家C的代表需求曲线 发展中国家的潜在出口品为低等品x 中等发达国家为中介品y产品中的e2e3出口给发展中国家 同时把e4e5出口给发达国家 而发达国家把z产品中的e5e6出口给中等发达国家 由于中等发达国家的需求结构既类似于发达国家 也类似于发展中国家 相互重叠的区间最大 且它们相互间的收入水平也相似 这类国家发展产业内贸易目前较好 故应加速向中等发达国家迈进 GravityModels Focustoexplainthevolume notthecomposition oftradebetweentwocountries Popularframeworkineconometrics Typicallythevolumeofexportsandimportsismodelledasafunctionofcountriesnationalincomes distanceandotherobservablecharacteristicssuchaspopulationsizeandinstitutionaldummies e g freetradearea GravityModels 引力模型在国际贸易的作用的最简单的形式 是设定任意两个贸易伙伴出口量是他们国家收入的递增函数和他们国家之间距离的递减函数 使用Yi和Yj分别表示国家收入 Dij表示距离 货物X从i国家流通到j国家 用线性形式表达如 1 InXij a bInYi rInYj dInDija b r和d均表示常量 可使用贸易国发生在单个年份或几个年份的横截面的数据来估计 Dij是按照两国首都城市的距离来实际计算的 使用模糊变量去获得接触的效应 如文化和历史的相似性以及区域的一体化也是一种通常的做法 GeographyandTrade Firmsdecidethelocationofproductioninthepresenceofeconomiesofscale rationaleforconcentratingproduction imperfectcompetitiontransportationcost rationalefordecentralizingproduction Dynamiccomparativeadvantagemaybebasedoncoincidencethathassetoffacumulativeprocess Tradeoftentakesplaceasaresultof arbitraryspecializationbasedonincreasedreturns Policiesmayinfluencethebeginningofsuchancumulativeprocess BasisforTrade ComparativeAdvantageTechnology RicardianModel Factorendowments Heckscher OhlinModel I