ChapFirmsinCompetitiveMarkets完全競爭市場

會計學(xué)1ChapFirmsinCompetitiveMarkets完全競爭市場TheMeaningofCompetitionAsaresultofitscharacteristics,theperfectlycompetitivemarkethasthefollowingoutcomes:Theactionsofanysinglebuyerorsellerinthemarkethaveanegligibleimpactonthemarketprice.Eachbuyerandsellertakesthemarketpriceasgiven.

第1頁/共57頁TheMeaningofCompetitionBuyersandsellersincompetitivemarketsaresaidtobepricetakers（價格接受者）.

Buyersandsellersmustacceptthepricedeterminedbythemarket.第2頁/共57頁Revenue（收益）ofaCompetitiveFirmTotalrevenueforafirmisthesellingpricetimesthequantitysold.TR=(PXQ)第3頁/共57頁RevenueofaCompetitiveFirmTotalrevenueisproportional（成比例的）totheamountofoutput.第4頁/共57頁RevenueofaCompetitiveFirmAveragerevenuetellsushowmuchrevenueafirmreceivesforthetypicalunitsold.第5頁/共57頁RevenueofaCompetitiveFirmInperfectcompetition,

averagerevenue

（平均收益）equalsthepriceofthegood.第6頁/共57頁RevenueofaCompetitiveFirmMarginalrevenue

（邊際收益）isthechangeintotalrevenuefromanadditionalunitsold.MR=TR/Q第7頁/共57頁RevenueofaCompetitiveFirmForcompetitivefirms,marginalrevenueequalsthepriceofthegood.第8頁/共57頁Total,Average,andMarginalRevenueforaCompetitiveFirm第9頁/共57頁ProfitMaximizationfortheCompetitiveFirmThegoalofacompetitivefirmistomaximizeprofit（利潤最大化）.Thismeansthatthefirmwillwanttoproducethequantitythatmaximizesthedifferencebetweentotalrevenueandtotalcost.第10頁/共57頁ProfitMaximization:

ANumericalExample第11頁/共57頁

P=AR=MR

P=MR1MCProfitMaximizationfortheCompetitiveFirm...Quantity0CostsandRevenueATCAVCQMAXThefirmmaximizesprofitbyproducingthequantityatwhichmarginalcostequalsmarginalrevenue.MC1Q1MC2Q2第12頁/共57頁ProfitMaximizationfortheCompetitiveFirmProfitmaximizationoccursatthequantitywheremarginalrevenueequalsmarginalcost.第13頁/共57頁ProfitMaximizationfortheCompetitiveFirmWhenMR>MCincreaseQWhenMR<MCdecreaseQWhenMR=MCProfitismaximized.第14頁/共57頁TheMarginal-CostCurveandtheFirm’sSupplyDecision...Quantity0CostsandRevenueMCATCAVCQ1

P1

P2Q2Thissectionofthefirm’sMCcurveisalsothefirm’ssupplycurve.第15頁/共57頁TheFirm’sShort-RunDecisiontoShutDown（關(guān)閉）Ashutdownreferstoashort-rundecisionnottoproduceanythingduringaspecific（特定的）periodoftimebecauseofcurrentmarketconditions.Exitreferstoalong-run（長期的）decisiontoleavethemarket.第16頁/共57頁TheFirm’sShort-RunDecisiontoShutDownThefirmconsidersitssunkcosts（沉沒成本）whendecidingtoexit,butignoresthemwhendecidingwhethertoshutdown.Sunkcostsarecoststhathavealreadybeencommittedandcannotberecovered.第17頁/共57頁TheFirm’sShort-RunDecisiontoShutDownThefirmshutsdowniftherevenueitgetsfromproducingislessthanthevariablecostofproduction.ShutdownifTR<VCShutdownifTR/Q<VC/QShutdownifP<AVC第18頁/共57頁TheFirm’sShort-RunDecisiontoShutDown...QuantityATCAVC0CostsMCIfP<AVC,

shutdown.IfP>AVC,keepproducingintheshortrun.IfP>ATC,keepproducingataprofit.Firm’sshort-runsupplycurve.第19頁/共57頁TheFirm’sShort-RunDecisiontoShutDownTheportion（部分）ofthemarginal-costcurvethatliesaboveaveragevariablecost（可變成本）isthecompetitivefirm’sshort-runsupplycurve（曲線）.第20頁/共57頁TheFirm’sLong-RunDecisiontoExitorEnteraMarketInthelong-run,thefirmexitsiftherevenueitwouldgetfromproducingislessthanitstotalcost.ExitifTR<TCExitifTR/Q<TC/QExitifP<ATC第21頁/共57頁TheFirm’sLong-RunDecisiontoExitorEnteraMarketAfirmwillentertheindustryifsuchanactionwouldbeprofitable.

EnterifTR>TCEnterifTR/Q>TC/QEnterifP>ATC第22頁/共57頁TheCompetitiveFirm’sLong-RunSupplyCurve...QuantityMC=Long-runSATCAVC0CostsFirmentersifP>ATCFirmexitsifP<ATC第23頁/共57頁TheCompetitiveFirm’sLong-RunSupplyCurveThecompetitivefirm’slong-runsupplycurveistheportionofitsmarginal-costcurvethatliesaboveaveragetotalcost.第24頁/共57頁TheCompetitiveFirm’sLong-RunSupplyCurve...QuantityMCATCAVC0CostsFirm’slong-runsupplycurve第25頁/共57頁TheFirm’sShort-RunandLong-RunSupplyCurvesShort-RunSupplyCurveTheportionofitsmarginalcostcurvethatliesaboveaveragevariablecost.Long-RunSupplyCurveThemarginalcostcurveabovetheminimumpointofitsaveragetotalcostcurve.第26頁/共57頁ProfitQMeasuringProfitintheGraphfortheCompetitiveFirm...Quantity0PriceP=AR=MRATCMCPATCProfit-maximizingquantitya.AFirmwithProfits第27頁/共57頁LossMeasuringProfitintheGraphfortheCompetitiveFirm...Quantity0PriceP=AR=MRATCMCPQLoss-minimizingquantityATCb.AFirmwithLosses第28頁/共57頁SupplyinaCompetitiveMarketMarketsupplyequalsthesumofthequantitiessuppliedbytheindividualfirmsinthemarket.第29頁/共57頁TheShortRun:MarketSupplywithaFixedNumberofFirmsForanygivenprice,eachfirmsuppliesaquantityofoutputsothatitsmarginalcostequalsprice.Themarketsupplycurvereflects（反映）theindividualfirms’marginalcostcurves.第30頁/共57頁TheShortRun:MarketSupplywithaFixedNumberofFirms...(a)IndividualFirmSupplyQuantity(firm)0Price(b)MarketSupplyQuantity(market)Price0SupplyMC1.00$2.001002001.00$2.00100,000200,000第31頁/共57頁TheLongRun:MarketSupplywithEntryandExitFirmswillenterorexitthemarketuntilprofitisdriventozero.Inthelongrun,priceequalstheminimumofaveragetotalcost.Thelong-runmarketsupplycurveishorizontal（水平的）atthisprice.第32頁/共57頁TheLongRun:MarketSupplywithEntryandExit...(a)Firm’sZero-ProfitConditionQuantity(firm)0Price

P=minimum

ATC(b)MarketSupplyQuantity(market)Price0SupplyMCATC第33頁/共57頁TheLongRun:MarketSupplywithEntryandExitAttheendoftheprocessofentryandexit,firmsthatremainmustbemakingzeroeconomicprofit.Theprocessofentry&exitendsonlywhenpriceandaveragetotalcostaredriventoequality.Long-runequilibrium（均衡）musthavefirmsoperatingattheirefficientscale.第34頁/共57頁FirmsStayinBusinesswithZeroProfitProfitequalstotalrevenueminustotalcost.Totalcostincludesalltheopportunitycostsofthefirm.Inthezero-profitequilibrium,thefirm’srevenuecompensatestheownersforthetimeandmoneytheyexpendtokeepthebusinessgoing.第35頁/共57頁IncreaseinDemandintheShortRunAnincreaseindemandraisespriceandquantityintheshortrun.Firmsearnprofitsbecausepricenowexceedsaveragetotalcost.第36頁/共57頁IncreaseinDemandintheShortRun...MarketFirmQuantity(firm)0PriceMCATCP1Quantity(market)Price0D1P1Q1AS1Long-runsupply(a)InitialCondition（初始情形）P第37頁/共57頁D2IncreaseinDemandintheShortRun...MarketFirmQuantity(firm)0PriceMCATCP1Quantity(market)Price0D1P1Q1AS1Long-runsupply(b)Short-RunResponse（短期的反應(yīng)）Q2BP2P2Profit第38頁/共57頁IncreaseinDemandintheShortRun...MarketFirmQuantity(firm)0PriceMCATCP1Quantity(market)Price0D1P1Q1AS1Long-runsupply(c)Long-RunResponse（長期的反應(yīng)）D2BQ2P2S2CQ3第39頁/共57頁SummaryBecauseacompetitivefirmisapricetaker

（價格接受者）,itsrevenueisproportionaltotheamountofoutputitproduces.Thepriceofthegoodequalsboththefirm’saveragerevenueanditsmarginalrevenue（邊際收益）.第40頁/共57頁SummaryTomaximizeprofitafirmchoosesthequantityofoutputsuchthatmarginalrevenueequalsmarginalcost.

Thisisalsothequantityatwhichpriceequalsmarginalcost.Therefore,thefirm’smarginalcostcurveisitssupplycurve.第41頁/共57頁SummaryIntheshortrunwhenafirmcannotrecoveritsfixedcosts,thefirmwillchoosetoshutdown（關(guān)閉）temporarily（暫時）ifthepriceofthegoodislessthanaveragevariablecost.Inthelongrunwhenthefirmcanrecoverbothfixedandvariablecosts,itwillchoosetoexitifthepriceislessthanaveragetotalcost.第42頁/共57頁SummaryInamarketwithfreeentryandexit,profitsaredriventozerointhelongrunandallfirmsproduceattheefficientscale.Changesindemandhavedifferenteffectsoverdifferenttimehorizons.第43頁/共57頁GraphicalReview第44頁/共57頁ProfitMaximizationfortheCompetitiveFirm...

P=AR=MR

P=MR1MCQuantity0CostsandRevenueATCAVCQMAXThefirmmaximizesprofitbyproducingthequantityatwhichmarginalcostequalsmarginalrevenue.MC1Q1MC2Q2Harcourt,Inc.itemsandderiveditemscopyright?2001byHarcourt,Inc.第45頁/共57頁TheMarginal-CostCurveandtheFirm’sSupplyDecision...Quantity0CostsandRevenueMCATCAVCQ1

P1

P2Q2Thissectionofthefirm’sMCcurveisalsothefirm’ssupplycurve.第46頁/共57頁TheFirm’sShort-RunDecisiontoShutDown...QuantityATCAVC0CostsMCIfP<AVC,

shutdown.IfP>AVC,keepproducingintheshortrun.IfP>ATC,keepproducingataprofit.Firm’sshort-runsupplycurve.第47頁/共57頁TheCompetitiveFirm’sLong-RunSupplyCurve...QuantityMC=Long-runSATCAVC0CostsFirmentersifP>ATCFirmexitsifP<ATC第48頁/共57頁TheCompetitiveFirm’sLong-RunSupplyCurve...QuantityMCATCAVC0CostsFirm’slong-runsupplycurve第49頁/共57頁MeasuringProfitintheGraphfortheCompetitiveFirm...ProfitQQuantity0PriceP=AR=MRATCMCPATCProfit-maximizingquantitya.AFirmwithProfits第50頁/共57頁MeasuringProfitintheGraphfortheCompetitiveFirm...LossQuantity0Pri