经济学（微观）（英文版原书第7版）课件 第13章　垄断竞争：更切实际的竞争模型

EconomicsSeventhEditionChapter13MonopolisticCompetition:TheCompetitiveModelinaMoreRealisticSettingCopyright©2019,2017,2015PearsonEducation,Inc.AllRightsReserved.ChapterOutline13.1

DemandandMarginalRevenueforaFirminaMonopolisticallyCompetitiveMarket13.2

HowaMonopolisticallyCompetitiveFirmMaximizesProfitintheShortRun13.3

WhatHappenstoProfitsintheLongRun?13.4

ComparingMonopolisticCompetitionandPerfectCompetition13.5

HowMarketingDifferentiatesProducts13.6

WhatMakesaFirmSuccessful?PerfectCompetitionvs.MonopolisticCompetitionTheperfectlycompetitivemarketsinthepreviouschapterhadthefollowingthreefeatures:ManyfirmsFirmssellidenticalproductsNobarrierstoentrytonewfirmsenteringtheindustryThefirsttwofeaturesimpliedahorizontaldemandcurveforindividualfirms,whilethethirdimpliedzerolong-runprofit.Monopolisticallycompetitivefirmssharefeatures1.and3.;buttheirproductsarenotidenticaltotheircompetitors’.Soweexpectmonopolisticallycompetitivefirmstohavezerolong-runprofitbutnottofaceahorizontaldemandcurve.13.1DemandandMarginalRevenueforaFirminaMonopolisticallyCompetitiveMarketExplainwhyamonopolisticallycompetitivefirmhasdownward-slopingdemandandmarginalrevenuecurves.Monopolisticcompetitionisamarketstructureinwhichbarrierstoentryarelowandmanyfirmscompetebysellingsimilar,butnotidentical,products.Thekeyfeaturehereisthattheproductsthatmonopolisticallycompetitivefirmssellaredifferentiatedfromoneanotherinsomeway.Example:Paneracompetesinthefast-casualrestaurantmarketwithfirmslikeChipotleandShakeShack.TheproductsPaneraanditscompetitorssellaredifferentiatedratherthanidentical.Figure13.1TheDownward-SlopingDemandCurveforTurkeySandwichesatPaneraPanerasellssandwiches;whileotherfirmsalsosellsandwiches,somecustomershaveapreferenceforPanerasandwiches.SoifPaneraraisesitsprice,somebutnotallofitscustomerswillswitchtobuyingtheirsandwicheselsewhere.ThismeansPanerafacesadownward-slopingdemandcurve.Table13.1DemandandMarginalRevenueataPaneraRestaurantSandwichesSoldperWeek(Q)Price(P)TotalRevenueAverageRevenueMarginalRevenue0$10.00$0.00——19.509.50$9.50$9.5029.0018.009.008.5038.5025.508.507.5048.0032.008.006.5057.5037.507.505.5067.0042.007.004.5076.5045.506.503.5086.0048.006.002.5095.5049.505.501.50105.0050.005.000.50114.5049.504.50−0.50ThefirsttwocolumnsshowthedemandscheduleforPanera.Totalrevenueincreasesinitially,thendecreases;Panerahastolowerthepriceinordertoselladditionalsandwiches.Somarginalrevenueisinitiallypositive,thennegative.Figure13.2HowaPriceCutAffectsaFirm’sRevenue(1of2)WhenPanerareducesthepriceofasandwich,itsells(let’ssay)1moresandwich.Itsrevenueincreasesbecauseoftheextrasale;thisistheoutputeffectofthepricereduction.Butitsrevenuedecreasesalso;tosellanothersandwich,itreducesthepriceonallsandwiches.Itloses$0.50inrevenueoneachofthesandwichesitwouldhavesoldanywayat$7.50.Thisisthepriceeffectofthepricereduction.Figure13.2HowaPriceCutAffectsaFirm’sRevenue(2of2)Panera’smarginalrevenueforsellingtheextrasandwichisequaltothegreenareaminusthepinkarea:theoutputeffectminusthepriceeffect.Theoutputeffectisequaltotheprice;somarginalrevenueislowerthantheprice.Foranyfirmwithadownward-slopingdemandcurve,itsmarginalrevenuecurvemustbebelowitsdemandcurve.Figure13.3TheDemandandMarginalRevenueCurvesforaMonopolisticallyCompetitiveFirmThegraphshowsthePanera’sdemandandmarginalrevenuecurvesforsandwiches.Afterthetenthsandwich,reducingthepriceinordertoincreasesalesresultsinrevenuedecreasing(negativemarginalrevenue).Thepriceeffectbecomeslargerthantheoutputeffect.13.2HowaMonopolisticallyCompetitiveFirmMaximizesProfitintheShortRunExplainhowamonopolisticallycompetitivefirmmaximizesprofitintheshortrun.Justlikeaperfectlycompetitivefirm,amonopolisticallycompetitivefirmshouldnotsimplytrytomaximizerevenue.Eachadditionalunitofoutputincurssomemarginalcost.Profitmaximizationrequiresproducinguntilthemarginalrevenuefromthelastunitisjustequaltothemarginalcost:MC=MR.Thissameruleholdsforallfirmsthatcanmarginallyadjusttheiroutput.Figure13.4MaximizingProfitinaMonopolisticallyCompetitiveMarket(1of3)Thefirst,second,third,andfourthsandwicheseachincreaseprofit:MC<MR.The5thdoesnotalterprofit:MC=MR.The6thandsubsequentsandwichesdecreaseprofit:MC>MR.Figure13.4MaximizingProfitinaMonopolisticallyCompetitiveMarket(2of3)PanerasellssandwichesupuntilMC=MR.Thisselectstheprofit-maximizingquantity.Thenthedemandcurveshowstheprice,andtheATCcurveshowstheaveragecost.SinceProfit=(P−ATC)×Q,wecanshowprofitonthegraphwiththegreenrectangle.Figure13.4MaximizingProfitinaMonopolisticallyCompetitiveMarket(3of3)Toidentifyprofit:UseMC=MRtoidentifytheprofit-maximizingquantity.Drawaverticallineatthatquantity.Theverticallinewillhitthedemandcurve:thisistheprice.TheverticallinewillalsohittheATCcurve:thisistheaveragecost.Thedifferencebetweenpriceandaveragecostistheprofit(orloss)perunit.Showtheprofitorlosswiththerectanglewithheight(P−ATC)andlength(Q*−0),whereQ*istheoptimalquantity.13.3WhatHappenstoProfitsintheLongRun?Analyzethesituationofamonopolisticallycompetitivefirminthelongrun.Whenafirmhastotalrevenuegreaterthantotalcost,itmakesaneconomicprofit.Thiseconomicprofitgivesentrepreneursanincentivetoenterthemarket.Inourpreviousexample,Paneramakesaneconomicprofit.Weexpectnewfirmstoenterthefast-casualsandwichmarket.ThesenewfirmswillreducethedemandforPanera’ssandwiches.Figure13.5HowEntryofNewFirmsEliminatesProfitsAtfirst(leftpanel),Panerahasfewcompetitors,sodemandforitssandwichesishigh.Itmakesaneconomicprofit.Thiseconomicprofitattractsnewfirms,decreasingthedemandforPanera’ssandwiches(rightpanel).ThiscontinuesuntilPaneranolongermakesaneconomicprofit.Table13.2TheShortRunandtheLongRunforaMonopolisticallyCompetitiveFirm(1of3)Intheshortrun,amonopolisticallycompetitivefirmmightmakeaprofitoraloss.Thesituationwherethefirmismakingaprofitisabove.Noticethattherearequantitiesforwhichdemand(price)isaboveATC;thisiswhatallowsthefirmtomakeaprofit.Table13.2TheShortRunandtheLongRunforaMonopolisticallyCompetitiveFirm(2of3)Nowthefirmismakingaloss.Noticethatthereisnownoquantityforwhichdemand(price)isaboveATC;thisfirmmustmakea(short-run)economicloss,nomatterwhatquantityitchooses.Table13.2TheShortRunandtheLongRunforaMonopolisticallyCompetitiveFirm(3of3)Inthelongrun,thefirmmustbreakeven.NoticethattheATCcurveisjusttangenttothedemandcurve.Thebestthefirmcandoistoproducethatquantity.Thereisnoquantityatwhichthefirmcanmakeaprofit;theATCcurveisneverbelowthedemandcurve.ZeroProfitintheLongRun?Ourmodelofmonopolisticcompetitionpredictsthatfirmswillearnzeroprofitinthelongrun.Howeverfirmsneednotpassivelyacceptthislong-runoutcome.Theycould:Innovatesothattheircostsarelowerthanotherfirms,orConvincetheircustomersthattheirproduct/experienceisbetterthanthatofotherfirms,eitherbyactuallymakingitbetterinsomeuniquewayormakingcustomersperceivethatitisbetter,perhapsthroughadvertising.Thinkofthelong-runas“thedirectionoftrend”;demandwillcontinuetofalltothezero(economic)profitlevel,unlessthefirmisabletodosomethingaboutit.ApplytheConcept:CanPaneraMaintainItsEconomicProfitwith“CleanFood”?PaneraCEORonShaich:“[Cleanfood]meanszeroartificialflavors,preservatives,sweetenersorcolorsfromnon-naturallyoccurringsourcesinanyfoodinourrestaurantsintheU.S.”Will“cleanfood”allowPaneratocontinueearningpositiveeconomicprofits?Onlyif:ConsumerdemandforthisfoodishighenoughtoallowhighpricesatPanera,andPanera’scompetitorscannoteffectivelycopyitsstrategy.Whatdoyouthink?13.4ComparingMonopolisticCompetitionandPerfectCompetitionComparetheefficiencyofmonopolisticcompetitionandperfectcompetition.Lastchapterwelearnedthatperfectlycompetitivefirmsachievedproductive

and

allocativeefficiency.Productive

efficiency

referstoproducingitemsatthelowestpossiblecost.Allocativeefficiencyreferstoproducingallgoodsuptothepointwherethemarginalbenefittoconsumersisjustequaltothemarginalcosttofirms.Monopolisticcompetitionresultsinneitherproductivenorallocativeefficiency.Figure13.6ComparingLong-RunEquilibriumunderPerfectCompetitionandMonopolisticCompetition(1of3)Inpanel(a),aperfectlycompetitivefirminlong-runequilibriumproducesatQPC,wherepriceequalsmarginalcost,andaveragetotalcostisataminimum.Theperfectlycompetitivefirmisbothallocativelyefficientandproductivelyefficient.Figure13.6ComparingLong-RunEquilibriumunderPerfectCompetitionandMonopolisticCompetition(2of3)Monopolisticallycompetitivefirmsinpanel(b)producethequantitywhereMC=MR.Themarginalbenefittoconsumersisgivenbythedemandcurve,soMC≠MB:notallocativelyefficient.Figure13.6ComparingLong-RunEquilibriumunderPerfectCompetitionandMonopolisticCompetition(3of3)Andaveragecostisaboveitsminimumpoint:notproductivelyefficient.Amonopolisticallycompetitivefirmhasexcesscapacity:ifitincreaseditsoutput,itcouldproduceataloweraveragetotalcost.IsMonopolisticCompetitionBadforConsumers?Thelackofefficiencysuggeststhatmonopolisticcompetitionisabadsituationforconsumers.Butconsumersmightbenefitfromtheproductdifferentiation.Example:Ifyouwerebuyingacar,wouldyoupreferoneProducedandsoldatthelowestpossiblecostbutnotwell-suitedtoyourtastesandpreferences;orProducedandsoldatahighercostbutdesignedtoattractyoutopurchasingit?Manyconsumersarewillingtoacceptahigherpriceforadifferentiatedproduct.Somonopolisticcompetitionisnotnecessarilybadforconsumers.ApplytheConcept:DifferentiateYourRestaurantbyBecomingaGhost!In2017GreenSummitGroupoperatednine“restaurants”inNYCandanothernineinChicago.Theyhadnobrick-and-mortarlocation;foodwasavailableonlythroughtheGrubHubapp.Thisbusinessmodelallowsforuniquemenuoptionsadaptingquicklytochangesinconsumertastes.13.5HowMarketingDifferentiatesProductsDefinemarketingandexplainhowfirmsusemarketingtodifferentiatetheirproducts.Makingcustomersbelievethatyourproductisworthwhileanddifferentfromthoseofotherfirmsisnotatrivialexercise.Ittypicallyinvolvessomedegreeofmarketing.Marketing:Alltheactivitiesnecessaryforafirmtosellaproducttoaconsumer.Onceafirmmanagestodifferentiateitsproduct,itmustcontinuetodosoorriskheadingtowardthelong-runoutcomeofzeroeconomicprofit.Theprocessofdoingthisisknownasbrandmanagement.Brandmanagement:Theactionsofafirmintendedtomaintainthedifferentiationofaproductovertime.AdvertisingAdvertisingisacriticalelementofmarketingformonopolisticallycompetitivefirms.Byadvertisingeffectively,firmscanincreasedemandfortheirproducts.Buttheycanalsouseadvertisingtodifferentiatetheirproducts:effectivelymakingthedemandcurvemoreinelastic.Thisallowsfirmstochargeahigherpriceandearnmoreshort-runprofit.DefendingaBrandNameMarketingexpertsandpsychologistsagree:acriticalaspectofmarketingiscreatingabrandnameforyourproduct.Asuccessfulbrandnamecanhelptomaintainproductdifferentiationanddelaytheabilityofotherfirmstocompeteawayyourprofits.Butfirmsmustalwaystrytomaintaintheperceptionoftheirproductasbetterthanothers,makingsurethat,forexample:Ahighly-successfulnamelikeCoke,Xerox,orBand-Aidisuniquelyassociatedtothatproductandnottogener