FirmsinCompetitiveMarkets

競(jìng)爭(zhēng)市場(chǎng)中的企業(yè)Chapter14WHATISACOMPETITIVEMARKET?

Aperfectlycompetitivemarkethasthefollowingcharacteristics:Therearemanybuyersandsellersinthemarket.Thegoodsofferedbythevarioussellersarelargelythesame.Firmscanfreelyenterorexitthemarket.什么是競(jìng)爭(zhēng)市場(chǎng)？完全競(jìng)爭(zhēng)市場(chǎng)有以下特點(diǎn):市場(chǎng)中有許多買(mǎi)者和許多賣(mài)者。各個(gè)賣(mài)者所提供的物品大體上是相同的。企業(yè)可以自由地進(jìn)入或退出市場(chǎng)。WHATISACOMPETITIVEMARKET?Asaresultofitscharacteristics,theperfectlycompetitivemarkethasthefollowingoutcomes:Theactionsofanysinglebuyerorsellerinthemarkethaveanegligibleimpactonthemarketprice.Eachbuyerandsellertakesthemarketpriceasgiven.

什么是競(jìng)爭(zhēng)市場(chǎng)？由于以上特點(diǎn),完全競(jìng)爭(zhēng)市場(chǎng)具有以下結(jié)果:市場(chǎng)上任何一個(gè)買(mǎi)者或賣(mài)者的行動(dòng)對(duì)市場(chǎng)價(jià)格的影響都可以忽略不計(jì)。每一個(gè)買(mǎi)者和賣(mài)者都把市場(chǎng)價(jià)格作為既定的。WHATISACOMPETITIVEMARKET?Acompetitivemarkethasmanybuyersandsellerstradingidenticalproductssothateachbuyerandsellerisapricetaker.Buyersandsellersmustacceptthepricedeterminedbythemarket.什么是競(jìng)爭(zhēng)市場(chǎng)?競(jìng)爭(zhēng)市場(chǎng)有許多買(mǎi)者和賣(mài)者交易相同的產(chǎn)品，所以每個(gè)買(mǎi)者和賣(mài)者都是價(jià)格接受者。買(mǎi)者和賣(mài)者必須接受市場(chǎng)決定的價(jià)格。TheRevenueofaCompetitiveFirm

競(jìng)爭(zhēng)企業(yè)的收益Totalrevenueforafirmisthesellingpricetimesthequantitysold.一個(gè)企業(yè)的總收益等于銷(xiāo)售價(jià)格乘以銷(xiāo)售量。TR=(PXQ)TheRevenueofaCompetitiveFirm

競(jìng)爭(zhēng)企業(yè)的收益Totalrevenueisproportionaltotheamountofoutput.總收益與產(chǎn)量同比例變化。TheRevenueofaCompetitiveFirmAveragerevenuetellsushowmuchrevenueafirmreceivesforthetypicalunitsold.Averagerevenueistotalrevenuedividedbythequantitysold.競(jìng)爭(zhēng)企業(yè)的收益平均收益告訴我們企業(yè)從普通一個(gè)單位產(chǎn)品銷(xiāo)售中得到了多少收益。平均收益等于總收益除以銷(xiāo)售量。TheRevenueofaCompetitiveFirmInperfectcompetition,

averagerevenueequalsthepriceofthegood.競(jìng)爭(zhēng)企業(yè)的收益在完全競(jìng)爭(zhēng)市場(chǎng),

平均收益等于物品的價(jià)格。TheRevenueofaCompetitiveFirm

競(jìng)爭(zhēng)企業(yè)的收益Marginalrevenueisthechangeintotalrevenuefromanadditionalunitsold.邊際收益是增加一個(gè)單位銷(xiāo)售量所引起的總收益變化。MR=

TR/

QTheRevenueofaCompetitiveFirm

競(jìng)爭(zhēng)企業(yè)的收益Forcompetitivefirms,marginalrevenueequalsthepriceofthegood.對(duì)競(jìng)爭(zhēng)企業(yè)來(lái)說(shuō)，邊際收益等于物品的銷(xiāo)售價(jià)格。Table1Total,Average,andMarginalRevenueforaCompetitiveFirm表1.競(jìng)爭(zhēng)企業(yè)的總收益、平均收益和邊際收益ProfitMaximizationandtheCompetitiveFirm’sSupplyCurveThegoalofacompetitivefirmistomaximizeprofit.Thismeansthatthefirmwillwanttoproducethequantitythatmaximizesthedifferencebetweentotalrevenueandtotalcost.利潤(rùn)最大化與競(jìng)爭(zhēng)企業(yè)的供給曲線競(jìng)爭(zhēng)企業(yè)的目標(biāo)是利潤(rùn)最大化。這就意味著企業(yè)想生產(chǎn)某一產(chǎn)量，使總收益與總成本的差最大。Table2ProfitMaximization:

ANumericalExampleCopyright?2004South-Western表2.利潤(rùn)最大化:一個(gè)數(shù)字例子Figure1ProfitMaximizationfor

aCompetitiveFirmCopyright?2004South-WesternQuantity0CostsandRevenueMCATCAVCMC1Q1MC2Q2Thefirmmaximizesprofitbyproducingthequantityatwhichmarginalcostequalsmarginalrevenue.QMAX

P=MR1=MR2

P=AR=MR

P=AR=MR

P=MR1MC圖1.競(jìng)爭(zhēng)企業(yè)的利潤(rùn)最大化產(chǎn)量0成本和收益ATCAVCQMAX通過(guò)生產(chǎn)邊際成本等于邊際收益的產(chǎn)量，企業(yè)使利潤(rùn)最大化MC1Q1MC2Q2ProfitMaximizationfortheCompetitiveFirm

競(jìng)爭(zhēng)企業(yè)的利潤(rùn)最大化Profitmaximizationoccursatthequantitywheremarginalrevenueequalsmarginalcost.當(dāng)邊際收益等于邊際成本時(shí)，企業(yè)實(shí)現(xiàn)利潤(rùn)最大化。ProfitMaximizationfortheCompetitiveFirmWhenMR>MC

increaseQWhenMR<MCdecreaseQWhenMR=MCProfitismaximized.競(jìng)爭(zhēng)企業(yè)的利潤(rùn)最大化當(dāng)MR>MC時(shí)，增加產(chǎn)量

Q當(dāng)MR<MC時(shí)，

減少產(chǎn)量Q當(dāng)MR=MC時(shí)，利潤(rùn)最大Figure2MarginalCostastheCompetitiveFirm’sSupplyCurveQuantity0PriceMCATCAVCP1Q1P2Q2Thissectionofthefirm’sMCcurveisalsothefirm’ssupplycurve.圖2.作為競(jìng)爭(zhēng)企業(yè)供給曲線的邊際成本產(chǎn)量0成本和收益MCATCAVCQ1

P1

P2Q2企業(yè)的這部分邊際成本曲線也是企業(yè)的供給曲線TheFirm’sShort-RunDecisiontoShutDownAshutdownreferstoashort-rundecisionnottoproduceanythingduringaspecificperiodoftimebecauseofcurrentmarketconditions.Exitreferstoalong-rundecisiontoleavethemarket.企業(yè)的短期停止?fàn)I業(yè)決策停止?fàn)I業(yè)是指在某個(gè)特殊時(shí)期由于當(dāng)前的市場(chǎng)條件而不生產(chǎn)任何東西的短期決策。退出是指離開(kāi)市場(chǎng)的長(zhǎng)期決策。TheFirm’sShort-RunDecisiontoShutDownThefirmconsidersitssunkcostswhendecidingtoexit,butignoresthemwhendecidingwhethertoshutdown.Sunkcostsarecoststhathavealreadybeencommittedandcannotberecovered.企業(yè)的短期停止?fàn)I業(yè)決策當(dāng)決定退出時(shí)，企業(yè)考慮沉淀成本；當(dāng)決定是否停止?fàn)I業(yè)時(shí)企業(yè)應(yīng)忽略沉淀成本。沉淀成本是已經(jīng)發(fā)生而且無(wú)法收回（并與當(dāng)前決策無(wú)關(guān)）的成本。TheFirm’sShort-RunDecisiontoShutDownThefirmshutsdowniftherevenueitgetsfromproducingislessthanthevariablecostofproduction.ShutdownifTR<VCShutdownifTR/Q<VC/QShutdownifP<AVC企業(yè)的短期停止?fàn)I業(yè)決策如果生產(chǎn)能得到的收益小于生產(chǎn)的可變成本，企業(yè)就停止?fàn)I業(yè)。如果TR<VC，停止?fàn)I業(yè)。如果TR/Q<VC/Q，停止?fàn)I業(yè)。如果P<AVC，停止?fàn)I業(yè)。Figure3TheCompetitiveFirm’sShortRunSupplyCurveMCQuantityATCAVC0CostsFirmshutsdownifP<AVCFirm’sshort-runsupplycurveIfP>AVC,firmwillcontinuetoproduceintheshortrun.IfP>ATC,thefirmwillcontinuetoproduceataprofit.圖3.競(jìng)爭(zhēng)企業(yè)的短期供給曲線產(chǎn)量ATCAVC0成本MC如果P<AVC,

停止?fàn)I業(yè)如果P>AVC,短期內(nèi)繼續(xù)生產(chǎn)如果P>ATC,繼續(xù)生產(chǎn)可以獲得利潤(rùn)企業(yè)短期供給曲線TheFirm’sShort-RunDecisiontoShutdown

企業(yè)的短期停止?fàn)I業(yè)決策Theportionofthemarginal-costcurvethatliesaboveaveragevariablecostisthecompetitivefirm’sshort-runsupplycurve.競(jìng)爭(zhēng)企業(yè)的短期供給曲線是邊際成本曲線在平均可變成本曲線以上的那一部分。TheFirm’sLong-RunDecisiontoExitorEnteraMarketInthelong-run,thefirmexitsiftherevenueitwouldgetfromproducingislessthanitstotalcost.ExitifTR<TCExitifTR/Q<TC/QExitifP<ATC企業(yè)進(jìn)入或退出一個(gè)市場(chǎng)的長(zhǎng)期決策在長(zhǎng)期中，如果從生產(chǎn)中得到的收益小于生產(chǎn)的總成本,企業(yè)就退出。如果TR<TC，就退出。如果TR/Q<TC/Q，就退出。如果P<ATC，就退出。TheFirm’sLong-RunDecisiontoExitorEnteraMarketAfirmwillentertheindustryifsuchanactionwouldbeprofitable.

EnterifTR>TCEnterifTR/Q>TC/QEnterifP>ATC企業(yè)進(jìn)入或退出一個(gè)市場(chǎng)的長(zhǎng)期決策如果一種行動(dòng)將有利可圖，企業(yè)就將進(jìn)入一個(gè)市場(chǎng)。如果TR>TC，就進(jìn)入。如果TR/Q>TC/Q，就進(jìn)入。如果P>ATC，就進(jìn)入。Figure4TheCompetitiveFirm’sLong-RunSupplyCurve

競(jìng)爭(zhēng)企業(yè)的長(zhǎng)期供給曲線Quantity產(chǎn)量MC=Long-runS企業(yè)長(zhǎng)期供給曲線ATCAVC0Costs成本FirmentersifP>ATC如果P>ATC，企業(yè)進(jìn)入FirmexitsifP<ATC如果P<ATC，企業(yè)退出THESUPPLYCURVEINACOMPETITIVEMARKET

競(jìng)爭(zhēng)市場(chǎng)的供給曲線Thecompetitivefirm’slong-runsupplycurveistheportionofitsmarginal-costcurvethatliesaboveaveragetotalcost.競(jìng)爭(zhēng)企業(yè)的長(zhǎng)期供給曲線是邊際成本曲線位于平均總成本曲線之上的那一部分。Figure4TheCompetitiveFirm’s

Long-RunSupplyCurve

競(jìng)爭(zhēng)企業(yè)的長(zhǎng)期供給曲線Quantity產(chǎn)量MCATCAVC0Costs成本Firm’slong-runsupplycurve企業(yè)長(zhǎng)期供給曲線THESUPPLYCURVE

INACOMPETITIVEMARKETShort-RunSupplyCurveTheportionofitsmarginalcostcurvethatliesaboveaveragevariablecost.Long-RunSupplyCurveThemarginalcostcurveabovetheminimumpointofitsaveragetotalcostcurve.競(jìng)爭(zhēng)市場(chǎng)的供給曲線短期供給曲線邊際成本曲線在平均可變成本曲線以上的那一部分。長(zhǎng)期供給曲線邊際成本曲線位于平均總成本曲線之上的那一部分。Figure5ProfitastheAreabetweenPrice

andAverageTotalCost(a)AFirmwithProfitsQuantity0PriceP=AR=

MRATCMCPATCQ(profit-maximizingquantity)Profit利潤(rùn)Q圖5.作為價(jià)格與平均總成本之間面積的利潤(rùn)產(chǎn)量0價(jià)格P=AR=MRATCMCPATC利潤(rùn)最大化產(chǎn)量a.有利潤(rùn)企業(yè)Figure5ProfitastheAreabetweenPrice

andAverageTotalCost(b)AFirmwithLossesQuantity0PriceATCMC(loss-minimizingquantity)P=AR=

MRPATCQLoss虧損圖5.作為價(jià)格與平均總成本之間面積的利潤(rùn)產(chǎn)量0價(jià)格P=AR=MRATCMCPQ虧損最小化產(chǎn)量ATCb.虧損企業(yè)SupplyinaCompetitiveMarket

競(jìng)爭(zhēng)市場(chǎng)的供給Marketsupplyequalsthesumofthequantitiessuppliedbytheindividualfirmsinthemarket.市場(chǎng)供給等于市場(chǎng)中個(gè)別企業(yè)的供給量之和。TheShortRun:MarketSupplywithaFixedNumberofFirmsForanygivenprice,eachfirmsuppliesaquantityofoutputsothatitsmarginalcostequalsprice.Themarketsupplycurvereflectstheindividualfirms’marginalcostcurves.短期：有固定數(shù)量企業(yè)的市場(chǎng)供給在任何一種既定價(jià)格時(shí)，個(gè)別企業(yè)供給量是使邊際成本等于價(jià)格時(shí)的產(chǎn)量。

市場(chǎng)供給曲線反映了個(gè)別企業(yè)的邊際成本曲線。Figure6MarketSupplywithaFixed

NumberofFirms(a)IndividualFirmSupplyQuantity(firm)0PriceMC1.00100$2.00200(b)MarketSupplyQuantity(market)0PriceSupply1.00100,000$2.00200,000圖6.有固定數(shù)量企業(yè)的市場(chǎng)供給(a)個(gè)別企業(yè)供給產(chǎn)量(企業(yè))0價(jià)格(b)市場(chǎng)供給產(chǎn)量(市場(chǎng))價(jià)格0供給MC1.00$2.001002001.00$2.00100,000200,000TheLongRun:MarketSupplywithEntryandExitFirmswillenterorexitthemarketuntilprofitisdriventozero.Inthelongrun,priceequalsthe minimumofaveragetotalcost.Thelong-runmarketsupplycurveishorizontalatthisprice.長(zhǎng)期：有進(jìn)入與退出的市場(chǎng)供給企業(yè)進(jìn)入或退出市場(chǎng)，直到經(jīng)濟(jì)利潤(rùn)為零。在長(zhǎng)期中，價(jià)格等于最小平均總成本。長(zhǎng)期市場(chǎng)供給曲線是這一價(jià)格時(shí)的水平線。利潤(rùn)Q圖5.作為價(jià)格與平均總成本之間面積的利潤(rùn)產(chǎn)量0價(jià)格P=AR=MRATCMCPATC利潤(rùn)最大化產(chǎn)量a.有利潤(rùn)企業(yè)——新企業(yè)進(jìn)入市場(chǎng)虧損圖5.作為價(jià)格與平均總成本之間面積的利潤(rùn)產(chǎn)量0價(jià)格P=AR=MRATCMCPQ虧損最小化產(chǎn)量ATCb.虧損企業(yè)——退出市場(chǎng)Figure7MarketSupplywithEntryandExit(a)Firm’sZero-ProfitConditionQuantity(firm)0Price(b)MarketSupplyQuantity(market)Price0P=minimumATCSupplyMCATC圖7.有進(jìn)入與退出的市場(chǎng)供給(a)企業(yè)零利潤(rùn)狀態(tài)產(chǎn)量(企業(yè))0價(jià)格

P=最小

ATC(b)市場(chǎng)供給產(chǎn)量(市場(chǎng))價(jià)格0供給MCATCTheLongRun:MarketSupplywithEntryandExitAttheendoftheprocessofentryandexit,firmsthatremainmustbemakingzeroeconomicprofit.Theprocessofentry&exitendsonlywhenpriceandaveragetotalcostaredriventoequality.Long-runequilibriummusthavefirmsoperatingattheirefficientscale.長(zhǎng)期：有進(jìn)入與退出的市場(chǎng)供給在這種進(jìn)入和退出過(guò)程結(jié)束時(shí)，仍然留在市場(chǎng)中的企業(yè)必定得到零經(jīng)濟(jì)利潤(rùn)。只有當(dāng)價(jià)格與平均總成本被推向相等時(shí)，進(jìn)入與退出過(guò)程才結(jié)束。競(jìng)爭(zhēng)市場(chǎng)長(zhǎng)期均衡一定是企業(yè)在其有效規(guī)模時(shí)運(yùn)行。WhyDoCompetitiveFirmsStayinBusinessIfTheyMakeZeroProfit?

Profitequalstotalrevenueminustotalcost.Totalcostincludesalltheopportunitycostsofthefirm.Inthezero-profitequilibrium,thefirm’srevenuecompensatestheownersforthetimeandmoneytheyexpendtokeepthebusinessgoing.如果競(jìng)爭(zhēng)企業(yè)獲得零利潤(rùn)，為什么它們還在經(jīng)營(yíng)？利潤(rùn)等于總收益減總成本。總成本包括企業(yè)的所有機(jī)會(huì)成本。在零利潤(rùn)均衡時(shí)，企業(yè)的收益應(yīng)該補(bǔ)償所有者期望用于使其企業(yè)維持的時(shí)間和金錢(qián)。AShiftinDemandintheShortRunandLongRun

短期與長(zhǎng)期的需求移動(dòng)Anincreaseindemandraisespriceandquantityintheshortrun.在短期內(nèi)，需求增加導(dǎo)致價(jià)格和數(shù)量上升。Firmsearnprofitsbecausepricenowexceedsaveragetotalcost.此時(shí)價(jià)格高于平均總成本，因此，企業(yè)賺到了正的經(jīng)濟(jì)利潤(rùn)。

Figure8AnIncreaseinDemandintheShortRunandLongRunFirm(a)InitialConditionQuantity(firm)0PriceMarketQuantity(market)Price0DDemand,1SShort-runsupply,1P1ATCLong-runsupplyP11QAMC圖8.短期與長(zhǎng)期需求增加市場(chǎng)企業(yè)產(chǎn)量(企業(yè))0價(jià)格MCATCP1產(chǎn)量(市場(chǎng))價(jià)格0D1，P1Q1AS1，長(zhǎng)期供給曲線(a)最初狀態(tài)P短期供給需求Figure8AnIncreaseinDemandintheShortRunandLongRunMarketFirm(b)Short-RunResponseQuantity(firm)0PriceMCATCProfitP1Quantity(market)Long-runsupplyPrice0D1D2P1S1P2Q1AQ2P2BD2圖8.短期與長(zhǎng)期需求增加市場(chǎng)企業(yè)產(chǎn)量(企業(yè))0價(jià)格MCATCP1產(chǎn)量(市場(chǎng))價(jià)格0D1P1Q1AS1長(zhǎng)期供給曲線(b)短期反應(yīng)Q2BP2P2利潤(rùn)Figure8AnIncreaseinDemandintheShortRunandLongRunP1Firm(c)Long-RunResponseQuantity(firm)0PriceMCATCMarketQuantity(market)Price0P1P2Q1Q2Long-runsupplyBD1D2S1AS2Q3C圖8.短期與長(zhǎng)期需求增加市場(chǎng)企業(yè)產(chǎn)量(企業(yè))0價(jià)格MCATCP1產(chǎn)量(市場(chǎng))價(jià)格0D1P1Q1AS1長(zhǎng)期供給曲線(c)長(zhǎng)期反應(yīng)D2BQ2P2S2CQ3WhytheLong-RunSupplyCurve

MightSlopeUpward

為什么長(zhǎng)期供給曲線會(huì)向右上方傾斜Someresourcesusedinproductionmaybeavailableonlyinlimitedquantities.

一些用于生產(chǎn)的資源數(shù)量可能是有限的Firmsmayhavedifferentcosts.

企業(yè)可能有不同的成本W(wǎng)hytheLong-RunSupplyCurve

MightSlopeUpward

為什么長(zhǎng)期供給曲線會(huì)向右上方傾斜MarginalFirm

邊際企業(yè)Themarginalfirmisthefirmthatwouldexitthemarketifthepricewereanylower.

邊際企業(yè)——如果價(jià)格有任何下降就退出市場(chǎng)的企業(yè)。SummaryBecauseacompetitivefirmisapricetaker,itsrevenueisproportionaltotheamountof