微观经济学-第八章.ppt

CHAPTER8OUTLINE 8 1PerfectlyCompetitiveMarkets8 2ProfitMaximization8 3MarginalRevenue MarginalCost andProfitMaximization8 4ChoosingOutputintheShortRun8 5TheCompetitiveFirm sShort RunSupplyCurve8 6TheShort RunMarketSupplyCurve8 7ChoosingOutputintheLongRun8 8TheIndustry sLong RunSupplyCurve PERFECTLYCOMPETITIVEMARKETS Themodelofperfectcompetitionrestsonthreebasicassumptions 1 pricetaking 2 producthomogeneity and 3 freeentryandexit PriceTaking Becauseeachindividualfirmsellsasufficientlysmallproportionoftotalmarketoutput itsdecisionshavenoimpactonmarketprice pricetakerFirmthathasnoinfluenceovermarketpriceandthustakesthepriceasgiven ProductHomogeneity Whentheproductsofallofthefirmsinamarketareperfectlysubstitutablewithoneanother thatis whentheyarehomogeneous nofirmcanraisethepriceofitsproductabovethepriceofotherfirmswithoutlosingmostorallofitsbusiness PERFECTLYCOMPETITIVEMARKETS FreeEntryandExit freeentry orexit Conditionunderwhichtherearenospecialcoststhatmakeitdifficultforafirmtoenter orexit anindustry WhenIsaMarketHighlyCompetitive Becausefirmscanimplicitlyorexplicitlycollude 或明或暗地串通 insettingprices thepresenceofmanyfirmsisnotsufficientforanindustrytoapproximateperfectcompetition Conversely thepresenceofonlyafewfirmsinamarketdoesnotruleoutcompetitivebehavior 股票市场是不是完全竞争 纽约证卷交易所的交易量约占上市公司股票总量的80 纳斯达克 Nasdaq 全国证卷经销商协会自动报价系统 是一个数千家未上市公司股票的电子交易系统 其股票是以及百家经纪商和经销商为基础进行的交易纳斯达克经销商也曾暗中共谋操纵股价 1997年12月 曾对美林公司 MerrillLynch Co 和花旗集团的索罗门 史密斯 巴尼公司进行10 3亿美元的罚款 PROFITMAXIMIZATION DoFirmsMaximizeProfit Theassumptionofprofitmaximizationisfrequentlyusedinmicroeconomicsbecauseitpredictsbusinessbehaviorreasonablyaccuratelyandavoidsunnecessaryanalyticalcomplications Forsmallerfirmsmanagedbytheirowners profitislikelytodominatealmostalldecisions Inlargerfirms however managerswhomakeday to daydecisionsusuallyhavelittlecontactwiththeowners i e thestockholders Inanycase firmsthatdonotcomeclosetomaximizingprofitarenotlikelytosurvive Firmsthatdosurviveincompetitiveindustriesmakelong runprofitmaximizationoneoftheirhighestpriorities AlternativeFormsofOrganization cooperativeAssociationofbusinessesorpeoplejointlyownedandoperatedbymembersformutualbenefit DoFirmsMaximizeProfit 追求利润是企业生存的必要条件 企业行为在短期内可能会偏离利润目标 但长期而言 在激烈竞争的市场上它就会被淘汰一个补贴公共电视台的企业似乎看起来是有公益精神和利他主义的 但这一慈善行为可能正是该企业的长期经济利益之所在 因为它给企业及其产品创造了商誉 MARGINALREVENUE MARGINALCOST ANDPROFITMAXIMIZATION profitDifferencebetweentotalrevenueandtotalcost q R q C q marginalrevenueChangeinrevenueresultingfromaone unitincreaseinoutput ProfitMaximizationintheShortRun Figure8 1 Afirmchoosesoutputq sothatprofit thedifferenceABbetweenrevenueRandcostC ismaximized Atthatoutput marginalrevenue theslopeoftherevenuecurve isequaltomarginalcost theslopeofthecostcurve q R q C q 0 MR q MC q 利润最大化的条件 Max q R q C q 方程对q求导 令其值为0d q dq dR q dq dC q dq 0dR q dq dC q dq利润最大时有 MR MC MARGINALREVENUE MARGINALCOST ANDPROFITMAXIMIZATION DemandandMarginalRevenueforaCompetitiveFirm DemandCurveFacedbyaCompetitiveFirm Figure8 2 Acompetitivefirmsuppliesonlyasmallportionofthetotaloutputofallthefirmsinanindustry Therefore thefirmtakesthemarketpriceoftheproductasgiven choosingitsoutputontheassumptionthatthepricewillbeunaffectedbytheoutputchoice In a thedemandcurvefacingthefirmisperfectlyelastic eventhoughthemarketdemandcurvein b isdownwardsloping MARGINALREVENUE MARGINALCOST ANDPROFITMAXIMIZATION Thedemanddcurvefacinganindividualfirminacompetitivemarketisbothitsaveragerevenuecurveanditsmarginalrevenuecurve Alongthisdemandcurve marginalrevenue averagerevenue andpriceareallequal ProfitMaximizationbyaCompetitiveFirm MC q MR P DemandandMarginalRevenueforaCompetitiveFirm CHOOSINGOUTPUTINTHESHORTRUN Short RunProfitMaximizationbyaCompetitiveFirm Marginalrevenueequalsmarginalcostatapointatwhichthemarginalcostcurveisrising OutputRule Ifafirmisproducinganyoutput itshouldproduceatthelevelatwhichmarginalrevenueequalsmarginalcost CHOOSINGOUTPUTINTHESHORTRUN TheShort RunProfitofaCompetitiveFirm ACompetitiveFirmMakingaPositiveProfit Figure8 3 Intheshortrun thecompetitivefirmmaximizesitsprofitbychoosinganoutputq atwhichitsmarginalcostMCisequaltothepriceP ormarginalrevenueMR ofitsproduct TheprofitofthefirmismeasuredbytherectangleABCD Anychangeinoutput whetherloweratq1orhigheratq2 willleadtolowerprofit 选择短期产量 MC MR处的产量水平使利润最大Q1处利润损失 AR MR P MC Q0 Q1 Q2 P Q Q2处还可以增加的利润为 竞争性厂商的短期赢利能力 平均利润 R Q C Q Q R Q Q C Q Q AR AC线段AB代表平均利润总利润 平均利润 产量为绿色矩形 AR MR P MC ATC Q0 A B CHOOSINGOUTPUTINTHESHORTRUN TheShort RunProfitofaCompetitiveFirm ACompetitiveFirmIncurringLosses Figure8 4 AcompetitivefirmshouldshutdownifpriceisbelowAVC Thefirmmayproduceintheshortrunifpriceisgreaterthanaveragevariablecost Shut DownRule Thefirmshouldshutdownifthepriceoftheproductislessthantheaveragevariablecostofproductionattheprofit maximizingoutput 何时退出行业 当PAVC 企业还会继续产生当P AVC时 企业退出该行业 MC P MR ATC AVC Q Q0 0 CHOOSINGOUTPUTINTHESHORTRUN Howshouldthemanagerdeterminetheplant sprofitmaximizingoutput Recallthatthesmeltingplant sshort runmarginalcostofproductiondependsonwhetheritisrunningtwoorthreeshiftsperday TheShort RunOutputofanAluminumSmeltingPlant Figure8 5 Intheshortrun theplantshouldproduce600tonsperdayifpriceisabove 1140pertonbutlessthan 1300perton Ifpriceisgreaterthan 1300perton itshouldrunanovertimeshiftandproduce900tonsperday Ifpricedropsbelow 1140perton thefirmshouldstopproducing butitshouldprobablystayinbusinessbecausethepricemayriseinthefuture 英贵族全球寻亲摇滚歌星获750万英镑庄园继承权 本杰明 史雷德男爵是英国萨默塞特郡汤顿市人 他的祖先曾是赫赫有名的贵族拥有一座祖传的13世纪古宅 曼索尔庄园 该庄园占地6 07平方公里 共有3个人工湖 养着430头家畜和13只孔雀 雇有5名工人照看 庄园中的豪华别墅里共有9个卧室 此外还有一间舞厅 一个图书馆 一个酒吧和5个可容纳80名宾客的大宴会厅 冲突乐队 TheFray 的26岁主唱艾萨克 史雷德幸运继承他价值750万英镑 约合1482万美元 的豪华庄园 曼索尔庄园的维护费用十分昂贵 仅一个月的供暖费用就需要1000英镑 1975美元 而本杰明却没有任何儿女继承人 一旦本杰明去世 曼索尔庄园将面临无人继承和照管的凄惨境地 本杰明称 事实上 只要有人愿意支付维护费用 并且照管好这个地方 我并不介意谁来继承它 但是我的亲戚都拥有自己的豪宅 没有一个人愿接受这样一座 旧房子 该庄园属于英国文物遗产 修理任何地方都必须报英国遗产部门批准 让许多富翁望而却步 THECOMPETITIVEFIRM SSHORT RUNSUPPLYCURVE Thefirm ssupplycurveistheportionofthemarginalcostcurveforwhichmarginalcostisgreaterthanaveragevariablecost TheShort RunSupplyCurveforaCompetitiveFirm Figure8 6 Intheshortrun thefirmchoosesitsoutputsothatmarginalcostMCisequaltopriceaslongasthefirmcoversitsaveragevariablecost Theshort runsupplycurveisgivenbythecrosshatchedportionofthemarginalcostcurve THECOMPETITIVEFIRM SSHORT RUNSUPPLYCURVE TheResponseofaFirmtoaChangeinInputPrice Figure8 7 Whenthemarginalcostofproductionforafirmincreases fromMC1toMC2 thelevelofoutputthatmaximizesprofitfalls fromq1toq2 Theshadedareainthefiguregivesthetotalsavingstothefirm orequivalently thereductioninlostprofit associatedwiththereductioninoutputfromq1toq2 TheShort RunProfitofaCompetitiveFirm THECOMPETITIVEFIRM SSHORT RUNSUPPLYCURVE Althoughplentyofcrudeoilisavailable theamountthatyourefinedependsonthecapacityoftherefineryandthecostofproduction TheShort RunProductionofPetroleumProducts Figure8 8 Astherefineryshiftsfromoneprocessingunittoanother themarginalcostofproducingpetroleumproductsfromcrudeoilincreasessharplyatseverallevelsofoutput Asaresult theoutputlevelcanbeinsensitivetosomechangesinpricebutverysensitivetoothers 短期供应曲线的移动 当投入要素价格变化时 同样产量水平的MC会改变 供应曲线将发生移动 D MC Q P 启示 竞争性厂商的短期赢利能力 价格是市场供求总量决定 企业是价格的接受者短期赢利能力决定于生产的企业的边际成本和平均成本进一步决定于生产要素的价格和企业技术和管理水平决定的要素的边际产品 定位在全球生产网络价值链的低端 处于市场 资金 品牌 技术全部依靠国外 而自己只是加工生产的发展状况一个芭比娃娃 在美国卖价是10美元 从中国出口的价格大约为3美元 其中头发进口于日本 橡胶来自东南亚 布料来自越南 中国只赚取0 35美元的加工费 没有价格决定能力 资源依赖型经济增长 以单位GDP产出能耗量表征的能源利用效率 我国与发达国家差距非常之大 日本为1 意大利为1 33 法国为1 5 德国为1 5 英国为2 17 美国为2 67 加拿大为3 5 而我国高达11 5 每吨标准煤的产出率 我国相当于美国的29 6 欧盟的16 8 日本的10 3 摘自中国城市环境卫生协会 环卫信息 对资源的定价能力低 同济大学教授 为什么我国作为铁矿石的一个重要采购大国却不具有对铁矿石价格的议价权 回答 1 铁矿石价格的谈判历史有30 40年 中国进入才3年 谈判规则是别人制定的 中国人目前只能执行 处于不利地位 2 价格谈判是三家对三家 中 日 英对巴西 澳大利亚的三家大矿山 日 英产品的附加值高 对价格上涨的承受力高 成本价格上涨对其最终产品价格的影响只有8 0 它们也希望借价格上涨打压中国企业 谈判不出力中国企业不团结 一方面价格谈判希望降价 另一方面有的企业又囤积购买 待价而沽 破坏谈判 P MC AC MC Q1 Q2 AC THESHORT RUNMARKETSUPPLYCURVE IndustrySupplyintheShortRun Theshort runindustrysupplycurveisthesummationofthesupplycurvesoftheindividualfirms Becausethethirdfirmhasaloweraveragevariablecostcurvethanthefirsttwofirms themarketsupplycurveSbeginsatpriceP1andfollowsthemarginalcostcurveofthethirdfirmMC3untilpriceequalsP2 whenthereisakink ForP2andallpricesaboveit theindustryquantitysuppliedisthesumofthequantitiessuppliedbyeachofthethreefirms Figure8 9 ElasticityofMarketSupply Es Q Q P P 价格上升对行业供应量的影响 产品价格上升有两种效应 产品供应量增加原材料成本上升 MC上升 供应曲线内移动 供应量降低 中国资源依赖型经济增长带动原材料价格上涨 进一步阻碍中国经济增长 行业供应曲线反应的是这两者的中和 THESHORT RUNMARKETSUPPLYCURVE Table8 1TheWorldCopperIndustry 2006 CountryAustraliaCanadaChileIndonesiaPeruPolandRussiaUSZambia Country9506005 4008001 0505307201 220540 AnnualProduction ThousandMetricTons Country1 151 300 800 900 851 200 650 850 75 MarginalCost DollarsPerPound SourceforAnnualProductionData U S GeologicalSurvey MineralCommoditySummaries January2007 http minerals usgs gov minerals pubs mcs 2007 mcs2007 pdf SourceforMarginalCostData CharlesRiverAssociates Estimates THESHORT RUNMARKETSUPPLYCURVE TheShort RunWorldSupplyofCopper Thesupplycurveforworldcopperisobtainedbysummingthemarginalcostcurvesforeachofthemajorcopper producingcountries Thesupplycurveslopesupwardbecausethemarginalcostofproductionrangesfromalowof65centsinRussiatoahighof 1 30inCanada Figure8 10 THESHORT RUNMARKETSUPPLYCURVE ProducerSurplusintheShortRun producersurplusSumoverallunitsproducedbyafirmofdifferencesbetweenthemarketpriceofagoodandthemarginalcostofproduction ProducerSurplusforaFirm Theproducersurplusforafirmismeasuredbytheyellowareabelowthemarketpriceandabovethemarginalcostcurve betweenoutputs0andq theprofit maximizingoutput Alternatively itisequaltorectangleABCDbecausethesumofallmarginalcostsuptoq isequaltothevariablecostsofproducingq Figure8 11 THESHORT RUNMARKETSUPPLYCURVE ProducerSurplusintheShortRun ProducerSurplusforaMarket Theproducersurplusforamarketistheareabelowthemarketpriceandabovethemarketsupplycurve between0andoutputQ Figure8 12 ProducerSurplusversusProfit Producersurplus PS R VC Profit R VC FC MC 生产者剩余 Q 0 P 生产者剩余为绿矩形面积生产者剩余 R Q VC Q AVC CHOOSINGOUTPUTINTHELONGRUN Long RunProfitMaximization OutputChoiceintheLongRun Thefirmmaximizesitsprofitbychoosingtheoutputatwhichpriceequalslong runmarginalcostLMC Inthediagram thefirmincreasesitsprofitfromABCDtoEFGDbyincreasingitsoutputinthelongrun Figure8 13 Thelong runoutputofaprofit maximizingcompetitivefirmisthepointatwhichlong runmarginalcostequalstheprice CHOOSINGOUTPUTINTHELONGRUN Long RunProfitMaximization OutputChoiceintheLongRun Thefirmmaximizesitsprofitbychoosingtheoutputatwhichpriceequalslong runmarginalcostLMC Inthediagram thefirmincreasesitsprofitfromABCDtoEFGDbyincreasingitsoutputinthelongrun Figure8 13 Thelong runoutputofaprofit maximizingcompetitivefirmisthepointatwhichlong runmarginalcostequalstheprice CHOOSINGOUTPUTINTHELONGRUN Long RunCompetitiveEquilibrium AccountingProfitandEconomicProfit R wL rK ZeroEconomicProfit zeroeconomicprofitAfirmisearninganormalreturnonitsinvestment i e itisdoingaswellasitcouldbyinvestingitsmoneyelsewhere CHOOSINGOUTPUTINTHELONGRUN Long RunCompetitiveEquilibrium EntryandExit Long RunCompetitiveEquilibrium Initiallythelong runequilibriumpriceofaproductis 40perunit shownin b astheintersectionofdemandcurveDandsupplycurveS1 In a weseethatfirmsearnpositiveprofitsbecauselong runaveragecostreachesaminimumof 30 atq2 PositiveprofitencouragesentryofnewfirmsandcausesashifttotherightinthesupplycurvetoS2 asshownin b Thelong runequilibriumoccursatapriceof 30 asshownin a whereeachfirmearnszeroprofitandthereisnoincentivetoenterorexittheindustry Figure8 14 厂商与市场的协调 Q P Q P D S1 AC MC S S2 S D P 厂商的情况 市场的情况 厂商的长期均衡 Q P Q P D S AC MC S S S D P 厂商的情况 市场的情况 D D 长期均衡 边际成本 平均成本 市场价格 CHOOSINGOUTPUTINTHELONGRUN Long RunCompetitiveEquilibrium EntryandExit Inamarketwithentryandexit afirmenterswhenitcanearnapositivelong runprofitandexitswhenitfacestheprospectofalong runloss long runcompetitiveequilibriumAllfirmsinanindustryaremaximizingprofit nofirmhasanincentivetoenterorexit andpriceissuchthatquantitysuppliedequalsquantitydemanded Along runcompetitiveequilibriumoccurswhenthreeconditionshold Allfirmsintheindustryaremaximizingprofit 2 Nofirmhasanincentiveeithertoenterorexittheindustrybecauseallfirmsareearningzeroeconomicprofit 3 Thepriceoftheproductissuchthatthequantitysuppliedbytheindustryisequaltothequantitydemandedbyconsumers CHOOSINGOUTPUTINTHELONGRUN Long RunCompetitiveEquilibrium FirmsHavingIdenticalCosts Toseewhyalltheconditionsforlong runequilibriummusthold assumethatallfirmshaveidenticalcosts Nowconsiderwhathappensiftoomanyfirmsentertheindustryinresponsetoanopportunityforprofit Theindustrysupplycurvewillshiftfurthertotheright andpricewillfall FirmsHavingDifferentCosts Nowsupposethatallfirmsintheindustrydonothaveidenticalcostcurves Thedistinctionbetweenaccountingprofitandeconomicprofitisimportanthere Ifapatentisprofitable otherfirmsintheindustrywillpaytouseit Theincreasedvalueofapatentthusrepresentsanopportunitycosttothefirmthatholdsit CHOOSINGOUTPUTINTHELONGRUN Long RunCompetitiveEquilibrium TheOpportunityCostofLand Thereareotherinstancesinwhichfirmsearningpositiveaccountingprofitmaybeearningzeroeconomicprofit Suppose forexample thataclothingstorehappenstobelocatednearalargeshoppingcenter Theadditionalflowofcustomerscansubstantiallyincreasethestore saccountingprofitbecausethecostofthelandisbasedonitshistoricalcost EconomicRent economicrentAmountthatfirmsarewillingtopayforaninputlesstheminimumamountnecessarytoobtainit CHOOSINGOUTPUTINTHELONGRUN Inthelongrun inacompetitivemarket theproducersurplusthatafirmearnsontheoutputthatitsellsconsistsoftheeconomicrentthatitenjoysfromallitsscarceinputs ProducerSurplusintheLongRun CHOOSINGOUTPUTINTHELONGRUN FirmsEarnZeroProfitinLong RunEquilibrium Inlong runequilibrium allfirmsearnzeroeconomicprofit In a abaseballteaminamoderate sizedcitysellsenoughticketssothatprice 7 isequaltomarginalandaveragecost In b thedemandisgreater soa 10pricecanbecharged Theteamincreasessalestothepointatwhichtheaveragecostofproductionplustheaverageeconomicrentisequaltotheticketprice Whentheopportunitycostassociatedwithowningthefranchise 专营权 istakenintoaccount theteamearnszeroeconomicprofit Figure8 15 ProducerSurplusintheLongRun THEINDUSTRY SLONG RUNSUPPLYCURVE Constant CostIndustry constant costindustryIndustrywhoselong runsupplycurveishorizontal Long RunSupplyinaConstant CostIndustry In b thelong runsupplycurveinaconstant costindustryisahorizontallineSL Whendemandincreases initiallycausingapricerise representedbyamovefrompointAtopointC thefirminitiallyincreasesitsoutputfromq1toq2 asshownin a Buttheentryofnewfirmscausesashifttotherightinindustrysupply Becauseinputpricesareunaffectedbytheincreasedoutputoftheindustry entryoccursuntiltheoriginalpriceisobtained atpointBin b Figure8 16 Thelong runsupplycurveforaconstant costindustryis therefore ahorizontallineatapricethatisequaltothelong runminimumaveragecostofproduction THEINDUSTRY SLONG RUNSUPPLYCURVE Increasing CostIndustry increasing costindustryIndustrywhoselong runsupplycurveisupwardsloping Long RunSupplyinanIncreasing CostIndustry In b thelong runsupplycurveinanincreasing costindustryisanupward slopingcurveSL Whendemandincreases initiallycausingapricerise thefirmsincreasetheiroutputfromq1toq2in a Inthatcase theentryofnewfirmscausesashifttotherightinsupplyfromS1toS2 Becauseinputpricesincreaseasaresult thenewlong runequilibriumoccursatahigherpricethantheinitialequilibrium Figure8 17 Inanincreasing costindustry thelong runindustrysupplycurveisupwardsloping 成本递减行业 投入品价格由于规模效应的影响将随着产量的增加而下降 MC线下移P3 P1SL向下倾斜 投入价格下降 技术进步 规模经济 范围经济 学习曲线 q1 P1 P3 q2 LAC1 SMC1 P2 q3 P1 Q1 D2 P2 Q2 P3 Q3 SL D1 S1 S2 THEINDUSTRY SLONG RUNSUPPLYCURVE Decreasing CostIndustry decreasing costindustryIndustrywhoselong runsupplycurveis