andInternationalTrade(发展经济学-厦门大学,陈涛

Chapter6EconomiesofScale,ImperfectCompetition,andInternationalTradeCopyright©2003PearsonEducation,Inc.Slide6-2IntroductionEconomiesofScaleandInternationalTrade:AnOverviewEconomiesofScaleandMarketStructureTheTheoryofImperfectCompetitionMonopolisticCompetitionandTradeDumpingTheTheoryofExternalEconomiesExternalEconomiesandInternationalTradeSummaryChapterOrganizationCopyright©2003PearsonEducation,Inc.Slide6-3IntroductionCountriesengageininternationaltradefortwobasicreasons:•Countriestradebecausetheydiffereitherintheirresourcesorintechnology.•Countriestradeinordertoachievescaleeconomiesorincreasingreturnsinproduction.Twomodelsofinternationaltradeinwhicheconomiesofscaleandimperfectcompetitionplayacrucialrole:•Monopolisticcompetitionmodel•DumpingmodelCopyright©2003PearsonEducation,Inc.Slide6-4EconomiesofScaleandInternationalTrade:AnOverviewModelsoftradebasedoncomparativeadvantage(e.g.Ricardianmodel)usedtheassumptionsofconstantreturnstoscaleandperfectcompetition:•Increasingtheamountofallinputsusedintheproductionofanycommoditywillincreaseoutputofthatcommodityinthesameproportion.Inpractice,manyindustriesarecharacterizedbyeconomiesofscale(alsoreferredtoasincreasingreturns).•Productionismostefficient,thelargerthescaleatwhichittakesplace.Copyright©2003PearsonEducation,Inc.Slide6-5Underincreasingreturnstoscale:•Outputgrowsproportionatelymorethantheincreaseinallinputs.•Averagecosts(costsperunit)declinewiththesizeofthemarket.EconomiesofScaleandInternationalTrade:AnOverviewCopyright©2003PearsonEducation,Inc.Slide6-6EconomiesofScaleandInternationalTrade:AnOverviewTable6-1:RelationshipofInputtoOutputforaHypotheticalIndustryCopyright©2003PearsonEducation,Inc.Slide6-7EconomiesofScaleandMarketStructureEconomiesofscalecanbeeither:•External–Thecostperunitdependsonthesizeoftheindustrybutnotnecessarilyonthesizeofanyonefirm.–Anindustrywilltypicallyconsistofmanysmallfirmsandbeperfectlycompetitive.•Internal–Thecostperunitdependsonthesizeofanindividualfirmbutnotnecessarilyonthatoftheindustry.–Themarketstructurewillbeimperfectlycompetitivewithlargefirmshavingacostadvantageoversmall.•Bothtypesofscaleeconomiesareimportantcausesofinternationaltrade.Copyright©2003PearsonEducation,Inc.Slide6-8Imperfectcompetition•Firmsareawarethattheycaninfluencethepriceoftheirproduct.–Theyknowthattheycansellmoreonlybyreducingtheirprice.•Eachfirmviewsitselfasapricesetter,choosingthepriceofitsproduct,ratherthanapricetaker.•Thesimplestimperfectlycompetitivemarketstructureisthatofapuremonopoly,amarketinwhichafirmfacesnocompetition.TheTheoryofImperfectCompetitionCopyright©2003PearsonEducation,Inc.Slide6-9Monopoly:ABriefReview•Marginalrevenue–Theextrarevenuethefirmgainsfromsellinganadditionalunit–Itscurve,MR,alwaysliesbelowthedemandcurve,D.–Inordertosellanadditionalunitofoutputthefirmmustlowerthepriceofallunitssold(notjustthemarginalone).TheTheoryofImperfectCompetitionCopyright©2003PearsonEducation,Inc.Slide6-10TheTheoryofImperfectCompetitionFigure6-1:MonopolisticPricingandProductionDecisionsDCost,CandPrice,PQuantity,QMonopolyprofitsACPMQMMRMCACCopyright©2003PearsonEducation,Inc.Slide6-11•MarginalRevenueandPrice–Marginalrevenueisalwayslessthantheprice.–Therelationshipbetweenmarginalrevenueandpricedependsontwothings:–Howmuchoutputthefirmisalreadyselling–Theslopeofthedemandcurve»Ittellsushowmuchthemonopolisthastocuthispricetosellonemoreunitofoutput.TheTheoryofImperfectCompetitionCopyright©2003PearsonEducation,Inc.Slide6-12–Assumethatthedemandcurvethefirmfacesisastraightline:Q=A–BxP(6-1)–ThentheMRthatthefirmfacesisgivenby:MR=P–Q/B(6-2)•AverageandMarginalCosts–AverageCost(AC)istotalcostdividedbyoutput.–MarginalCost(MC)istheamountitcoststhefirmtoproduceoneextraunit.TheTheoryofImperfectCompetitionCopyright©2003PearsonEducation,Inc.Slide6-13–Whenaveragecostsdeclineinoutput,marginalcostisalwayslessthanaveragecost.–Supposethecostsofafirm,C,taketheform:C=F+cxQ(6-3)–Thisisalinearcostfunction.–Thefixedcostinalinearcostfunctiongivesrisetoeconomiesofscale,becausethelargerthefirm’soutput,thelessisfixedcostperunit.–Thefirm’saveragecostsisgivenby:AC=C/Q=F/Q+c(6-4)TheTheoryofImperfectCompetitionCopyright©2003PearsonEducation,Inc.Slide6-14Figure6-2:AverageVersusMarginalCostTheTheoryofImperfectCompetitionAveragecostMarginalcost120345624681012141618202224CostperunitOutputCopyright©2003PearsonEducation,Inc.Slide6-15MonopolisticCompetition•Oligopoly–Internaleconomiesgenerateanoligopolymarketstructure.–Thereareseveralfirms,eachofwhichislargeenoughtoaffectprices,butnonewithanuncontestedmonopoly.–Strategicinteractionsamongoligopolistshavebecomeimportant.–Eachfirmdecidesitsownactions,takingintoaccounthowthatdecisionmightinfluenceitsrival’sactions.TheTheoryofImperfectCompetitionCopyright©2003PearsonEducation,Inc.Slide6-16•Monopolisticcompetition–Aspecialcaseofoligopoly–Twokeyassumptionsaremadetogetaroundtheproblemofinterdependence:–Eachfirmisassumedtobeabletodifferentiateitsproductfromitsrivals.–Eachfirmisassumedtotakethepriceschargedbyitsrivalsasgiven.TheTheoryofImperfect