Chap_17壟斷競爭(經濟學原理中英文雙語)MonopolisticCompetition

壟斷競爭Imperfectcompetitionreferstothosemarketstructuresthatfallbetweenperfectcompetitionandpuremonopoly.

不完全競爭是指介于完全競爭與純壟斷之間的市場結構。TheFourTypesofMarketStructureMonopoly（Chap15）Oligopoly(Chap16)MonopolisticCompetition(Chap17)PerfectCompetition（Chap14）

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NovelsMovies

WheatMilkNumberofFirms?TypeofProducts?ManyfirmsOnefirmFewfirmsDifferentiatedproductsIdenticalproducts市場結構的四種類型壟斷（15章）寡頭（16章）壟斷競爭（17章）完全競爭（14章）自來水

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牛奶企業數量?產品類型？許多企業一家企業幾家企業有差別產量相同產品TypesofImperfectlyCompetitiveMarketsMonopolisticCompetition

Manyfirmssellingproductsthataresimilarbutnotidentical.OligopolyOnlyafewsellers,eachofferingasimilaroridenticalproducttotheothers.不完全競爭市場的類型壟斷競爭

許多出售相似但不相同產品的企業組成的市場結構。寡頭只有很少賣者，出售相似或相同的產品。MonopolisticCompetition

壟斷競爭Marketsthathavesomefeaturesofcompetitionandsomefeaturesofmonopoly.有某些競爭特點又有某些壟斷特點的市場結構。AttributesofMonopolisticcompetition

壟斷競爭的特點Manysellers

很多賣者Productdifferentiation

產品有差異Freeentryandexit

自由進入和退出ManySellersTherearemanyfirmscompetingforthesamegroupofcustomers.Productexlesincludebooks,CDs, movies,computergames,restaurants, pianolessons,cookies,furniture,etc.很多賣者有許多企業爭奪同樣的顧客群體。產品例子包括書籍、CD、電影、電腦游戲、餐館、鋼琴課、點心、家居等等。ProductDifferentiationEachfirmproducesaproductthatisatleastslightlydifferentfromthoseofotherfirms.Ratherthanbeingapricetaker,eachfirmfacesadownward-slopingdemandcurve.產品差異化每個企業生產的一種產品至少與其他企業生產的這種產品略有不同。每個企業不是價格接受者，而是面臨一條向右下方傾斜的需求曲線。FreeEntryorExitFirmscanenterorexitthemarketwithoutrestriction.Thenumberoffirmsinthemarketadjustsuntileconomicprofitsarezero.自由進入或退出企業可以沒有限制地進入或退出一個市場。市場上企業的數量要一直調整到經濟利潤為零時為止。MonopolisticCompetitionintheShortRunShort-runeconomicprofitsencouragenewfirmstoenterthemarket.This:Increasesthenumberofproductsoffered.Reducesdemandfacedbyfirmsalreadyinthemarket.Incumbentfirms’demandcurvesshifttotheleft.Demandfortheincumbentfirms’productsfall,andtheirprofitsdecline.短期中的壟斷競爭企業短期經濟利潤激勵新企業進入市場。這種進入增加了顧客可以選擇的產品數量。減少了市場已有的每家企業面臨的需求。使市場已有企業面臨的需求曲線向左移動。市場已有企業的產品需求減少，利潤下降。Figure1MonopolisticCompetition

intheShortRunQuantity0PriceProfit-maximizingquantityPriceDemandMRATC(a)FirmMakesProfitAveragetotalcostProfitMC圖1.短期中的壟斷競爭企業(a)企業有利潤產量0價格需求MRATC利潤MC利潤最大化產量價格平均總成本MonopolisticCompetitionin

theShortRunShort-runeconomiclossesencouragefirmstoexitthemarket.This:

Decreasesthenumberofproductsoffered.Increasesdemandfacedbytheremainingfirms.Shiftstheremainingfirms’demandcurvestotheright.Increasestheremainingfirms’profits.短期中的壟斷競爭企業短期經濟虧損激勵企業退出市場。隨著企業退出：

顧客可選擇的產品數量少了。增加了繼續留在市場中的企業面臨的需求。使繼續留在市場中的企業的需求曲線向右移動。使繼續留在市場中的企業的利潤增加。Figure1MonopolisticCompetitors

intheShortRunDemandQuantity0PricePriceLoss-minimizingquantityAveragetotalcost(b)FirmMakesLossesMRLossesATCMC圖1.短期中的壟斷競爭企業產量0價格需求MR虧損(b)企業虧損MCATC平均總成本利潤最小化產量價格TheLong-RunEquilibrium

長期均衡Firmswillenterandexituntilthefirmsaremakingexactlyzeroeconomicprofits.企業進入或退出的過程一直持續到市場中的企業的經濟利潤正好是零時。Figure2AMonopolisticCompetitor

intheLongRunQuantityPrice0DemandMRATCMCProfit-maximizingquantityP=ATC圖2.長期中的壟斷競爭者產量價格0需求MRATCMC利潤最大化產量P=ATCLong-RunEquilibriumTwoCharacteristicsAsinamonopoly,priceexceedsmarginalcost.Profitmaximizationrequiresmarginalrevenuetoequalmarginalcost.Thedownward-slopingdemandcurvemakesmarginalrevenuelessthanprice.Asinacompetitivemarket,priceequalsaveragetotalcost.Freeentryandexitdriveeconomicprofittozero.長期均衡兩個特點正如在壟斷市場上一樣，價格大于邊際成本。利潤最大化要求邊際收益等于邊際成本。向右下方傾斜的需求曲線使邊際成本小于價格。正如在競爭市場上一樣，價格等于平均總成本。自由進入與退出使經濟利潤為零。MonopolisticversusPerfectCompetitionTherearetwonoteworthydifferencesbetweenmonopolisticandperfectcompetition—excesscapacityandmarkup.壟斷競爭與完全競爭壟斷競爭和完全競爭之間有兩個值得注意的差別—過剩生產能力和價格加成。MonopolisticversusPerfectCompetitionExcessCapacityThereisnoexcesscapacityinperfectcompetitioninthelongrun.Freeentryresultsincompetitivefirmsproducingatthepointwhereaveragetotalcostisminimized,whichistheefficientscaleofthefirm.Thereisexcesscapacityinmonopolisticcompetitioninthelongrun.Inmonopolisticcompetition,outputislessthantheefficientscaleofperfectcompetition.壟斷競爭與完全競爭過剩生產能力在長期中，完全競爭企業沒有過剩生產能力。競爭市場上的自由進入使企業生產平均總成本最小的產量，即企業的有效規模產量。在長期中，壟斷競爭企業存在過剩生產能力。壟斷競爭企業的產量低于完全競爭企業生產的有效規模產量。Figure3MonopolisticversusPerfectCompetitionQuantity0PriceDemand(a)MonopolisticallyCompetitiveFirmQuantity0PriceP=MCP=MR(demandcurve)(b)PerfectlyCompetitiveFirmMCATCMCATCMREfficientscalePQuantityproducedQuantityproduced=Efficientscale圖3.

壟斷競爭與完全競爭產量(a)壟斷競爭企業(b)完全競爭企業產量價格P=MR(需求曲線)MCATC價格需求MCATC過剩生產能力生產量有效規模P=MC產量=有效規模產量PMonopolisticversusPerfectCompetitionMarkupOverMarginalCostForacompetitivefirm,priceequalsmarginalcost.Foramonopolisticallycompetitivefirm,priceexceedsmarginalcost.Becausepriceexceedsmarginalcost,anextraunitsoldatthepostedpricemeansmoreprofitforthemonopolisticallycompetitivefirm.壟斷競爭與完全競爭高于邊際成本的價格加成對一個競爭企業來說，價格等于邊際成本。對一個壟斷競爭企業來說，價格高于邊際成本。因為壟斷競爭企業的價格高于其邊際成本，以牌價多銷售出一個單位產品就意味著利潤多了。Figure3MonopolisticversusPerfectCompetitionQuantity0PriceDemand(a)MonopolisticallyCompetitiveFirmQuantity0PriceP=MCP=MR(demandcurve)(b)PerfectlyCompetitiveFirmMarkupMCATCMCATCMRMarginalcostPQuantityproducedQuantityproduced圖3.高于邊際成本的價格加成產量(a)壟斷競爭企業(b)完全競爭企業產量價格P=MCP=MR(需求曲線)MCATC生產量價格P需求邊際成本MCATCMR價格加成生產量Figure3MonopolisticversusPerfectCompetitionQuantity0PriceDemand(a)MonopolisticallyCompetitiveFirmQuantity0PriceP=MCP=MR(demandcurve)(b)PerfectlyCompetitiveFirmMarkupExcesscapacityMCATCMCATCMRMarginalcostEfficientscalePQuantityproducedQuantityproduced=Efficientscale圖3.壟斷競爭和完全競爭產量(a)壟斷競爭企業(b)完全競爭企業產量價格P=MR(需求曲線)MCATC生產量有效規模價格P需求MCATCP=MC過剩市場能力邊際成本價格加成MR生產量=有效規模MonopolisticCompetitionandtheWelfareofSociety

壟斷競爭與社會福利Monopolisticcompetitiondoesnothaveallthedesirablepropertiesofperfectcompetition.壟斷競爭不具有完全競爭所具有的令人合意的特性。MonopolisticCompetitionandtheWelfareofSocietyThereisthenormaldeadweightlossofmonopolypricinginmonopolisticcompetitioncausedbythemarkupofpriceovermarginalcost.However,theadministrativeburdenofregulatingthepricingofallfirmsthatproducedifferentiatedproductswouldbeoverwhelming.壟斷競爭與社會福利壟斷競爭市場存在由于高于邊際成本的價格加成所導致的正常的無謂損失。但是，管制所有生產差異產品的企業的管理負擔將是巨大的。

MonopolisticCompetitionandtheWelfareofSocietyAnotherwayinwhichmonopolisticcompetitionmaybesociallyinefficientisthatthenumberoffirmsinthemarketmaynotbethe“ideal”one.Theremaybetoomuchortoolittleentry.壟斷競爭與社會福利壟斷競爭可能引起社會無效率的另一個方面是市場上的企業數量可能并不是“理想”的數量，可能有太多或太少的企業進入。MonopolisticCompetitionandtheWelfareofSociety

壟斷競爭與社會福利Externalitiesofentryinclude:進入的外部性包括：product-varietyexternalities.

產品多樣化外部性

business-stealingexternalities.

搶走業務的外部性MonopolisticCompetitionand

theWelfareofSocietyTheproduct-varietyexternality:Becauseconsumersgetsomeconsumersurplusfromtheintroductionofanewproduct,entryofanewfirmconveysapositiveexternalityonconsumers.Thebusiness-stealingexternality:Becauseotherfirmslosecustomersandprofitsfromtheentryofanewcompetitor,entryofanewfirmimposesanegativeexternalityonexistingfirms.壟斷競爭與社會福利產品多樣化外部性:由于消費者從新產品引進中得到了一些消費者剩余，所以存在與進入相關的正外部性。搶走業務的外部性:由于其它企業從與新進入者的競爭者中失去顧客和利潤，所以存在與進入相關的負外部性。Advertising廣告Whenfirmsselldifferentiatedproductsandchargepricesabovemarginalcost,eachfirmhasanincentivetoadvertiseinordertoattractmorebuyerstoitsparticularproduct.當企業銷售有差異產品并收取高于邊際成本的價格時，每個企業都有靠做廣告來吸引更多顧客購買自己特殊產品的激勵。AdvertisingFirmsthatsellhighlydifferentiatedconsumergoodstypicallyspendbetween10and20percentofrevenueonadvertising.Overall,about2percentoftotalrevenue,orover$100billionayear,isspentonadvertising.廣告銷售很大差異消費品的企業，通常都把收益的10％－20％用于廣告支出。總體上，廣告支出占企業總收益的2％左右,或者在1000億美元以上。Advertising廣告Criticsofadvertisingarguethatfirmsadvertiseinordertomanipulatepeople’stastes.

廣告的批評者認為，企業做廣告是為了操縱人們的嗜好。Theyalsoarguethatitimpedescompetitionbyimplyingthatproductsaremoredifferentthantheytrulyare.

批評者還認為，廣告抑制了競爭。廣告努力使消費者相信產品差異大于實際情況。AdvertisingDefendersarguethatadvertisingprovidesinformationtoconsumersTheyalsoarguethatadvertisingincreasescompetitionbyofferingagreatervarietyofproductsandprices.Thewillingnessofafirmtospendadvertisingdollarscanbeasignaltoconsumersaboutthequalityoftheproductbeingoffered.廣告廣告的辯護者認為，企業用廣告向顧客提供信息。辯護者還認為，廣告加劇了競爭，為顧客提供了更多的產品和價格。企業愿意用大量的錢來做廣告，這本身就向消費者傳遞了一個所提供產品質量的信息。BrandNames品牌Criticsarguethatbrandnamescauseconsumerstoperceivedifferencesthatdonotreallyexist.

品牌的批評者認為，品牌使消費者感覺到的產品差異大于實際存在的差異。BrandNamesEvidinginformationaboutquality.givingfirmsincentivetomaintainhighquality.品牌經濟學家對品牌的辯護是認為品牌是消費者保證他們購買的物品具有高質量的一種有用方法。提供產品質量信息。向企業提供了保持高質量的激勵。SummaryAmonopolisticallycompetitivemarketischaracterizedbythreeattributes:manyfirms,differentiatedproducts,andfr