管理經(jīng)濟(jì)學(xué)課件3

Demand,Supply,&MarketEquilibriumChenHongjunHenanUniversityofTechnologyChapter2

Demand,Supply,&MarketEq1MarketsandPricesWhydoesMingYAOearnmorethanChen(anawardwinningteacher)?MarketsandPricesWhydoesMin2MarketsandPricesWhydodiamondscostmorethanwater?MarketsandPricesWhydodiamo3MarketsandPricesWhydoQiBaiShi’s(齊白石)

crabssellformorethantherealones?MarketsandPricesWhydoQiBai4MarketsandPricesIsitcostofproductionthatdeterminesprices(asAdamSmiththought)?MarketsandPricesIsitcosto5MarketsandPricesOrisitwillingnesstopaythatdeterminesprices(asStanleyJevonsthought)?WilliamStanleyJevons(September1,1835-August13,1882),English

economistandlogician,wasborninLiverpool.MarketsandPricesOrisitwil6MarketsandPricesAlfredMarshall(PrinciplesofEconomics,1890)wasthefirsttoexplainclearlyhowbothcostsandwillingnesstopayinteracttodeterminemarketprices.MarketsandPricesAlfredMarsh7MarketsandPricesMarketsandPrices8WhatisaMarket?Amarketisanyarrangementthroughwhichbuyers&sellersexchangegoods&servicesMarketsreducetransactioncostsCostsofmakingatransactionotherthanthepriceofthegoodorserviceWhatisaMarket?Amarketisa9MarketStructuresMarketcharacteristicsthatdeterminetheeconomicenvironmentinwhichafirmoperatesNumber&sizeoffirmsinmarketDegreeofproductdifferentiationLikelihoodofnewfirmsenteringmarketMarketStructuresMarketcharac10PerfectCompetition

完全競爭LargenumberofrelativelysmallfirmsUndifferentiatedproductNobarrierstoentryPerfectCompetition

完全競爭Large11Monopoly完全壟斷SinglefirmProducesproductwithnoclosesubstitutesProtectedbyabarriertoentry如電力、電話、自來水、天然氣以及公共運(yùn)輸?shù)刃袠I(yè)。譬如，某人離家百米之內(nèi)有一小雜貨鋪，油鹽醬醋等日常生活用品一般在此購買。假定方圓10里之內(nèi)只有這么一家賣油鹽醬醋的小雜貨鋪，而一般推定人們往往不會為生活瑣事舍近求遠(yuǎn)，因此，這家小雜貨鋪實(shí)際上無異于一個(gè)處于完全壟斷地位的″壟斷企業(yè)″?？梢哉f小范圍的完全壟斷市場結(jié)構(gòu)是經(jīng)常存在的。Monopoly完全壟斷Singlef12MonopolisticCompetition

壟斷競爭LargenumberofrelativelysmallfirmsDifferentiatedproductsNobarrierstoentryMonopolisticCompetition

壟斷競爭L13納愛斯?fàn)I養(yǎng)維C牙膏

選一支好牙膏，給自己加一份健康保障。云南白藥牙膏，國家保密配方。”

冷熱酸甜，想吃就吃

納愛斯?fàn)I養(yǎng)維C牙膏選一支好牙膏，給自己加一份健康保障。云南14Oligopoly

寡頭壟斷FewfirmsproduceallormostofmarketoutputProfitsareinterdependentActionsbyanyonefirmwillaffectsales&profitsoftheotherfirms如美國汽車業(yè)的通用、福特和克萊斯勒，投資銀行業(yè)的美林、高盛和摩根斯坦利等Oligopoly

寡頭壟斷Fewf15DemandQuantitydemanded(Qd)Amountofagoodorserviceconsumersarewilling&abletopurchaseduringagivenperiodoftimeDemandQuantitydemanded(Qd)16DemandSixvariablesthatinfluenceQdPriceofgoodorservice(P)Incomesofconsumers(M.normal,inferior)Pricesofrelatedgoods&services(PR.)(substitutesandcomplements)Expectedfuturepriceofproduct(Pe)Numberofconsumersinmarket(N)Someexamplesofgoodsandservicesthatmightbeinferiorincludeshoerepairs,genericfoodproducts,andusedcars.DemandSixvariablesthatinflu17GeneralizedDemandFunctionb,c,d,e,f,&gareslopeparametersMeasureeffectonQd

ofchangingoneofthevariableswhileholdingtheothersconstantSignofparametershowshowvariableisrelatedtoQdPositivesignindicatesdirectrelationshipNegativesignindicatesinverserelationshipGeneralizedDemandFunction18GeneralizedDemandFunctionVariableRelationtoQdSignofSlopeParameterPPeNMPRInverseDirectDirectDirectDirectfornormalgoodsInverseforinferiorgoodsDirectforsubstitutesb=Qd/Pisnegativec=Qd/M

ispositivec=Qd/M

isnegatived=Qd/PR

ispositived=Qd/PR

isnegativef=Qd/Pe

ispositiveg=Qd/N

ispositiveInverseforcomplementse=Qd/

ispositiveGeneralizedDemandFunctionVar19DemandFunctionDemandfunction,ordemand,showsrelationbetweenP&Qd

whenallothervariablesareheldconstant

Qd=f(P)LawofDemandQd

increaseswhenPfalls&Qd

decreaseswhenPrises,allelseconstantQd/PmustbenegativeDemandFunctionDemandfunction20LawofDemand需求定律（TheLawofDemand）是說任何物品的價(jià)格下降，其需求量必定上升。古往今來，何時(shí)何地，不能有例外。這也是說，以豎線為價(jià)及豎線之下的橫線為量，其中的需求曲線一定是向右下傾斜的。

需求定律是經(jīng)濟(jì)學(xué)的靈魂，其重要性是不能夸大的。任何經(jīng)濟(jì)學(xué)論著，有道之士可單看作者對這定律的操縱就知道作者的斤兩如何。這定律不需要在文字上提到，但內(nèi)容上這定律要墨守成規(guī)——我在自己的博士論文《佃農(nóng)理論》上就刻意地完全不提“需求”，向老師表演一下。

--張五?！督?jīng)濟(jì)解釋》之十七

LawofDemand需求定律（TheLawofD21張五?？癜林?/p>

/u/11998399911935年生于香港，被譽(yù)為華人世界里最著名的經(jīng)濟(jì)學(xué)家，新制度經(jīng)濟(jì)學(xué)和現(xiàn)代產(chǎn)權(quán)經(jīng)濟(jì)學(xué)的創(chuàng)始人之一。

1982年起他擔(dān)任香港大學(xué)經(jīng)濟(jì)金融學(xué)院教授、院長，他的理論主張往往在學(xué)術(shù)界引起廣泛爭議。主要著作有《佃農(nóng)理論》（英文1969）、《社會成本的神話》（英文1978）、《中國會走向‘資本主義’的道路嗎？》（英文1982）、《賣橘者言》（1984）等等。一方面，張五常教授在理論上下過苦功，“由淺入深、由深轉(zhuǎn)復(fù)雜，再由復(fù)雜轉(zhuǎn)深、再轉(zhuǎn)淺，來來回回好幾次”，已把價(jià)格理論咀嚼透爛。另一方面，張五常注重案例研究，大量時(shí)間用于現(xiàn)實(shí)問題的實(shí)踐調(diào)查，多年礪煉，使他的學(xué)術(shù)素養(yǎng)和對現(xiàn)實(shí)問題的把握渾然一體。

他曾當(dāng)選美國西部經(jīng)濟(jì)學(xué)會會長，是第一位獲此職位的美國本土之外的學(xué)者。1969年以名為《佃農(nóng)理論——引證于中國的農(nóng)業(yè)及臺灣的土地改革》的博士論文轟動西方經(jīng)濟(jì)學(xué)界。1991年作為唯一一位未獲諾貝爾獎的經(jīng)濟(jì)學(xué)者而被邀請參加了當(dāng)年的諾貝爾頒獎典禮。

張五常狂傲之魅

22GraphingDemandCurvesTraditionallyprice(P)isplottedontheverticalaxis&quantitydemanded(Qd)isplottedonthehorizontalaxisTheequationplottedistheinversedemandfunctionP=f(Qd)GraphingDemandCurvesTraditio23GraphingDemandCurvesApointonademandcurveshowseither:MaximumamountofagoodthatwillbepurchasedforagivenpriceMaximumpriceconsumerswillpayforaspecificamountofthegoodGraphingDemandCurvesApoint24GraphingDemandCurvesChangeinquantitydemandedOccurswhenpricechangesMovementalongdemandcurveChangeindemandOccurswhenoneoftheothervariables,ordeterminantsofdemand,changesDemandcurveshiftsrightward

orleftwardGraphingDemandCurvesChangei25ShiftsinDemand

(Figure2.2)Qd01,100700100QuantityPrice(dollars)900P3005001,5001,3001020304050607080D0D1D2??$50,300$50,600??$40,200$40,500DemandincreaseDemanddecreaseShiftsinDemand(Figure26SupplyQuantitysupplied(Qs)AmountofagoodorserviceofferedforsaleduringagivenperiodoftimeSupplyQuantitysupplied(Qs)27SupplySixvariablesthatinfluenceQsPriceofgoodorservice(P)Inputprices(PI)Pricesofgoodsrelatedinproduction(Pr)Technologicaladvances(T)Expectedfuturepriceofproduct(Pe)Numberoffirmsproducingproduct(F)Generalizedsupplyfunction

SupplySixvariablesthatinflu28GeneralizedSupplyFunctionk,l,m,n,r,&sareslopeparametersMeasureeffectonQs

ofchangingoneofthevariableswhileholdingtheothersconstantSignofparametershowshowvariableisrelatedtoQsPositivesignindicatesdirectrelationshipNegativesignindicatesinverserelationshipGeneralizedSupplyFunction29GeneralizedSupplyFunctionVariableRelationtoQsSignofSlopeParameterPPeFPIPrDirectDirectDirectInverseInverseInverseforsubstitutesk=Qs/Pispositivel=Qs/PI

isnegativem=Qs/Pr

isnegativem=Qs/Pr

ispositiver=Qs/Pe

isnegatives=Qs/F

ispositiveDirectforcomplementsn=Qs/T

ispositiveTGeneralizedSupplyFunctionVar30SupplyFunctionSupplyfunction,orsupply,showsrelationbetweenP&Qs

whenallothervariablesareheldconstant

Qs=g(P)SupplyFunctionSupplyfunction31GraphingSupplyCurvesApointonasupplycurveshowseither:MaximumamountofagoodthatwillbeofferedforsaleatagivenpriceMinimumpricenecessarytoinduceproducerstovoluntarilyofferaparticularquantityforsaleGraphingSupplyCurvesApoint32GraphingSupplyCurvesChangeinquantitysuppliedOccurswhenpricechangesMovementalongsupplycurveChangeinsupplyOccurswhenoneoftheothervariables,ordeterminantsofsupply,changesSupplycurveshiftsrightwardorleftwardGraphingSupplyCurvesChangei33S0S2S1SupplydecreaseQs07001009003005001020304050607080ShiftsinSupply

(Figure2.4)QuantityPrice(dollars)P$60,700$60,400????$40,500$40,650SupplyincreaseS0S2S1SupplydecreaseQ34MarketEquilibriumEquilibriumprice&quantityaredeterminedbytheintersectionofdemand&supplycurvesAtthepointofintersection,Qd=QsConsumerscanpurchasealltheywant&producerscansellalltheywantatthe“market-clearing”priceMarketEquilibriumEquilibrium35S0MarketEquilibrium

(Figure2.5)Qd,Qs01,100700100QuantityPrice(dollars)900P3005001,5001,3001020304050607080D0?????S0MarketEquilibrium(Figur36ThemarketforlobstersThemarketforlobstersinZhengzhou,onJanuary20,2009.ThemarketforlobstersThemar37MarketEquilibriumQuantityandPriceEquilibriumoccursattheprice-quantitypairforwhichbothbuyersandsellersaresatisfied.Atthemarketequilibriumpriceof$6perlobster,buyersandsellersareeachabletobuyorsellasmanylobstersastheywishto.MarketEquilibriumQuantityan38D2D1S0DemandShifts(SupplyConstant)

(Figure2.6)Qd,Qs01,100700100QuantityPrice(dollars)900P3005001,5001,3001020304050607080D0???A?B?CD2D1S0DemandShifts(SupplyCo39DemandShiftsDemandShifts40S2S1S0SupplyShifts(DemandConstant)

(Figure2.7)Qd,Qs01,100700100QuantityPrice(dollars)900P3005001,3001020304050607080D0???R?S?TS2S1S0SupplyShifts(DemandCo41SimultaneousShiftsWhendemand&supplyshiftsimultaneouslyCanpredicteitherthedirectioninwhichpricechangesorthedirectioninwhichquantitychanges,butnotboth

Thechangeinequilibriumpriceorquantityissaidtobeindeterminatewhenthedirectionofchangedependsontherelativemagnitudesbywhichdemand&supplyshiftSimultaneousShiftsWhendemand42AChangeinSupplyAChangeinSupply43SD’S’’S’DSimultaneousShifts:

(D,S)QPricemayriseorfall;QuantityrisesP?AQPB?P’Q’Q’’C?P’’SD’S’’S’DSimultaneousShifts:44DSimultaneousShifts:

(D,S)SD’S’’S’QPricefalls;QuantitymayriseorfallP?AQPB?P’Q’Q’’C?P’’DSimultaneousShifts:(D,S)45S’’SimultaneousShifts:

(D,S)DSD’S’QPricerises;QuantitymayriseorfallP?AQPB?P’Q’Q’’C?P’’S’’SimultaneousShifts:(D,46SimultaneousShifts:

(D,S)S’’DSD’S’QPricemayriseorfall;QuantityfallsP?AQPB?P’Q’Q’’C?P’’SimultaneousShifts:(D,S)S47管理經(jīng)濟(jì)學(xué)課件348Ceiling&FloorPricesQxQuantityPrice(dollars)QxPxPxQuantityPrice(dollars)SxDx2501622233284PanelA–CeilingpriceSxDx250PanelB–FloorpriceCeiling&FloorPricesQxQuant49Excesssupply(FloorPrices)A

situationinwhichpriceexceedsitsequilibriumvalueiscalledoneofexcesssupply,or

surplus.At$8,thereisanexcesssupplyof2000lobstersinthismarket.Excesssupply(FloorPrices)A50ExcessDemandAsituationinwhichpriceliesbelowitsequilibriumvalueisreferredtoasoneofexcessdemand.Atapriceof$4inthislobstermarket,thereisanexcessdemandof2000lobsters.ExcessDemandAsituationinwh51ZeroexcesssupplyanddemandEquilibriumoccursattheprice-quantitypairforwhichbothbuyersandsellersaresatisfied.Atthemarketequilibriumpriceof$6,bothexcessdemandandexcesssupplyareexactlyzero..ZeroexcesssupplyanddemandE52Example3.1.Atapriceof$2inthishypotheticallobstermarket,howmuchexcessdemandforlobsterswilltherebe?Howmuchexcesssupplywilltherebeatapriceof$10?DDSS123450246810Price($/lobster)Quantity(1000lobsters/day)Example3.1.Atapriceof$2i53TheTradingLocusWhenpricediffersfromtheequilibriumprice,tradinginthemarketplacewillbeconstrained--bythebehaviorofbuyersifthepriceliesaboveequilibrium,bythebehaviorofsellersifbelow.TradinglocusTheTradingLocusWhenpricedi54FromdisequilibriumtoequilibriumAtpricesaboveequilibrium,sellersarenotsellingasmuchastheywantto.Theimpulseofadissatisfiedselleristoreducehisprice.Fromdisequilibriumtoequilib55FromdisequilibriumtoequilibriumAtpricesbelowtheequilibriumvalue,buyerscannotobtainthequantitiestheywishtopurchase.Somebuyersadjustbyofferingslightlyhigherprices.Fromdisequilibriumtoequilib56FromdisequilibriumtoequilibriumAnextraordinaryfeatureofthisequilibratingprocessisthatnooneconsciouslyplansordirectsit.Theactualstepsthatconsumersandproducersmusttaketomovetowardequilibriumareoftenindescribablycomplex.Supplierslookingtoexpandtheiroperations,forexample,mustchoosefromabewilderinglylargemenuofequipmentoptions.Buyers,fortheirpart,faceliterallymillionsofchoicesabouthowtospendtheirmoney.Fromdisequilibriumtoequilib57FromdisequilibriumtoequilibriumAndyettheadjustmenttowardequilibriumresultsmoreorlessautomaticallyfromthenaturalreactionsofself-interestedindividualsfacingeithersurplusesorshortages.Fromdisequilibriumtoequilib58Ceiling&FloorPricesCeilingpriceMaximumpricegovernmentpermitssellerstochargeforagoodWhenceilingpriceisbelowequilibrium,ashortageoccursFloorpriceMinimumpricegovernmentpermitssellerstochargeforagoodWhenfloorpriceisaboveequilibrium,asurplusoccursCeiling&FloorPricesCeiling59昆明市民呼吁米線限價(jià)律師支持政府干預(yù)_縣域經(jīng)濟(jì)_農(nóng)博網(wǎng)給牛肉面限價(jià)一些“心理”支持這幾天關(guān)于蘭州牛肉面限價(jià)的新聞已是鋪天蓋地，爭議聲四起，廣州日報(bào)7月1日的報(bào)道說：蘭州市物價(jià)局副局長魏立中在通報(bào)會上表示：牛肉面價(jià)格就是蘭州人心中的民生價(jià)格。

發(fā)表日期：2007年7月18日

潘石屹:限價(jià)房無法律支持

造成市場混亂

孫紅麗2008年12月12日11:33

來源：人民網(wǎng)-房產(chǎn)頻道化肥“限價(jià)令”遭遇執(zhí)行尷尬

國家發(fā)改委近日發(fā)布的《當(dāng)前化肥生產(chǎn)形勢應(yīng)予關(guān)注》報(bào)告稱，為了維護(hù)農(nóng)民利益，國家對化肥產(chǎn)品實(shí)行限價(jià)，但由于政府給予的化肥生產(chǎn)企業(yè)一些優(yōu)惠政策如化肥用煤炭限價(jià)落實(shí)不到位等問題，導(dǎo)致企業(yè)經(jīng)營生產(chǎn)困難，甚至虧損停產(chǎn)。該報(bào)告指出：“一旦化肥供給數(shù)量低于農(nóng)業(yè)需求，影響到農(nóng)業(yè)生產(chǎn)特別是糧食生產(chǎn)，將對糧食安全產(chǎn)生較大的負(fù)面影響?！辈⒔ㄗh有關(guān)部門適時(shí)調(diào)整政策取向和調(diào)控力度，為化肥行業(yè)與農(nóng)業(yè)的和諧發(fā)展創(chuàng)造條件。

在市場行為與限價(jià)政策杠桿的較量中，政策變得越來越“力不從心”，目前化肥市場正處于價(jià)格限又限不住、放又不敢放的尷尬局面。既然補(bǔ)貼農(nóng)資生產(chǎn)環(huán)節(jié)難以監(jiān)管，政府不妨借鑒給農(nóng)民發(fā)放糧食直補(bǔ)的做法，將過去對流通環(huán)節(jié)的間接補(bǔ)貼改為對農(nóng)民的直接補(bǔ)貼。

昆明市民呼吁米線限價(jià)律師支持政府干預(yù)_縣域經(jīng)濟(jì)_農(nóng)博網(wǎng)60Questions/CommentsThankyou!Questions/Comments61Demand,Supply,&MarketEquilibriumChenHongjunHenanUniversityofTechnologyChapter2

Demand,Supply,&MarketEq62MarketsandPricesWhydoesMingYAOearnmorethanChen(anawardwinningteacher)?MarketsandPricesWhydoesMin63MarketsandPricesWhydodiamondscostmorethanwater?MarketsandPricesWhydodiamo64MarketsandPricesWhydoQiBaiShi’s(齊白石)

crabssellformorethantherealones?MarketsandPricesWhydoQiBai65MarketsandPricesIsitcostofproductionthatdeterminesprices(asAdamSmiththought)?MarketsandPricesIsitcosto66MarketsandPricesOrisitwillingnesstopaythatdeterminesprices(asStanleyJevonsthought)?WilliamStanleyJevons(September1,1835-August13,1882),English

economistandlogician,wasborninLiverpool.MarketsandPricesOrisitwil67MarketsandPricesAlfredMarshall(PrinciplesofEconomics,1890)wasthefirsttoexplainclearlyhowbothcostsandwillingnesstopayinteracttodeterminemarketprices.MarketsandPricesAlfredMarsh68MarketsandPricesMarketsandPrices69WhatisaMarket?Amarketisanyarrangementthroughwhichbuyers&sellersexchangegoods&servicesMarketsreducetransactioncostsCostsofmakingatransactionotherthanthepriceofthegoodorserviceWhatisaMarket?Amarketisa70MarketStructuresMarketcharacteristicsthatdeterminetheeconomicenvironmentinwhichafirmoperatesNumber&sizeoffirmsinmarketDegreeofproductdifferentiationLikelihoodofnewfirmsenteringmarketMarketStructuresMarketcharac71PerfectCompetition

完全競爭LargenumberofrelativelysmallfirmsUndifferentiatedproductNobarrierstoentryPerfectCompetition

完全競爭Large72Monopoly完全壟斷SinglefirmProducesproductwithnoclosesubstitutesProtectedbyabarriertoentry如電力、電話、自來水、天然氣以及公共運(yùn)輸?shù)刃袠I(yè)。譬如，某人離家百米之內(nèi)有一小雜貨鋪，油鹽醬醋等日常生活用品一般在此購買。假定方圓10里之內(nèi)只有這么一家賣油鹽醬醋的小雜貨鋪，而一般推定人們往往不會為生活瑣事舍近求遠(yuǎn)，因此，這家小雜貨鋪實(shí)際上無異于一個(gè)處于完全壟斷地位的″壟斷企業(yè)″?？梢哉f小范圍的完全壟斷市場結(jié)構(gòu)是經(jīng)常存在的。Monopoly完全壟斷Singlef73MonopolisticCompetition

壟斷競爭LargenumberofrelativelysmallfirmsDifferentiatedproductsNobarrierstoentryMonopolisticCompetition

壟斷競爭L74納愛斯?fàn)I養(yǎng)維C牙膏

選一支好牙膏，給自己加一份健康保障。云南白藥牙膏，國家保密配方?！?/p>

冷熱酸甜，想吃就吃

納愛斯?fàn)I養(yǎng)維C牙膏選一支好牙膏，給自己加一份健康保障。云南75Oligopoly

寡頭壟斷FewfirmsproduceallormostofmarketoutputProfitsareinterdependentActionsbyanyonefirmwillaffectsales&profitsoftheotherfirms如美國汽車業(yè)的通用、福特和克萊斯勒，投資銀行業(yè)的美林、高盛和摩根斯坦利等Oligopoly

寡頭壟斷Fewf76DemandQuantitydemanded(Qd)Amountofagoodorserviceconsumersarewilling&abletopurchaseduringagivenperiodoftimeDemandQuantitydemanded(Qd)77DemandSixvariablesthatinfluenceQdPriceofgoodorservice(P)Incomesofconsumers(M.normal,inferior)Pricesofrelatedgoods&services(PR.)(substitutesandcomplements)Expectedfuturepriceofproduct(Pe)Numberofconsumersinmarket(N)Someexamplesofgoodsandservicesthatmightbeinferiorincludeshoerepairs,genericfoodproducts,andusedcars.DemandSixvariablesthatinflu78GeneralizedDemandFunctionb,c,d,e,f,&gareslopeparametersMeasureeffectonQd

ofchangingoneofthevariableswhileholdingtheothersconstantSignofparametershowshowvariableisrelatedtoQdPositivesignindicatesdirectrelationshipNegativesignindicatesinverserelationshipGeneralizedDemandFunction79GeneralizedDemandFunctionVariableRelationtoQdSignofSlopeParameterPPeNMPRInverseDirectDirectDirectDirectfornormalgoodsInverseforinferiorgoodsDirectforsubstitutesb=Qd/Pisnegativec=Qd/M

ispositivec=Qd/M

isnegatived=Qd/PR

ispositived=Qd/PR

isnegativef=Qd/Pe

ispositiveg=Qd/N

ispositiveInverseforcomplementse=Qd/

ispositiveGeneralizedDemandFunctionVar80DemandFunctionDemandfunction,ordemand,showsrelationbetweenP&Qd

whenallothervariablesareheldconstant

Qd=f(P)LawofDemandQd

increaseswhenPfalls&Qd

decreaseswhenPrises,allelseconstantQd/PmustbenegativeDemandFunctionDemandfunction81LawofDemand需求定律（TheLawofDemand）是說任何物品的價(jià)格下降，其需求量必定上升。古往今來，何時(shí)何地，不能有例外。這也是說，以豎線為價(jià)及豎線之下的橫線為量，其中的需求曲線一定是向右下傾斜的。

需求定律是經(jīng)濟(jì)學(xué)的靈魂，其重要性是不能夸大的。任何經(jīng)濟(jì)學(xué)論著，有道之士可單看作者對這定律的操縱就知道作者的斤兩如何。這定律不需要在文字上提到，但內(nèi)容上這定律要墨守成規(guī)——我在自己的博士論文《佃農(nóng)理論》上就刻意地完全不提“需求”，向老師表演一下。

--張五?！督?jīng)濟(jì)解釋》之十七

LawofDemand需求定律（TheLawofD82張五?？癜林?/p>

/u/11998399911935年生于香港，被譽(yù)為華人世界里最著名的經(jīng)濟(jì)學(xué)家，新制度經(jīng)濟(jì)學(xué)和現(xiàn)代產(chǎn)權(quán)經(jīng)濟(jì)學(xué)的創(chuàng)始人之一。

1982年起他擔(dān)任香港大學(xué)經(jīng)濟(jì)金融學(xué)院教授、院長，他的理論主張往往在學(xué)術(shù)界引起廣泛爭議。主要著作有《佃農(nóng)理論》（英文1969）、《社會成本的神話》（英文1978）、《中國會走向‘資本主義’的道路嗎？》（英文1982）、《賣橘者言》（1984）等等。一方面，張五常教授在理論上下過苦功，“由淺入深、由深轉(zhuǎn)復(fù)雜，再由復(fù)雜轉(zhuǎn)深、再轉(zhuǎn)淺，來來回回好幾次”，已把價(jià)格理論咀嚼透爛。另一方面，張五常注重案例研究，大量時(shí)間用于現(xiàn)實(shí)問題的實(shí)踐調(diào)查，多年礪煉，使他的學(xué)術(shù)素養(yǎng)和對現(xiàn)實(shí)問題的把握渾然一體。

他曾當(dāng)選美國西部經(jīng)濟(jì)學(xué)會會長，是第一位獲此職位的美國本土之外的學(xué)者。1969年以名為《佃農(nóng)理論——引證于中國的農(nóng)業(yè)及臺灣的土地改革》的博士論文轟動西方經(jīng)濟(jì)學(xué)界。1991年作為唯一一位未獲諾貝爾獎的經(jīng)濟(jì)學(xué)者而被邀請參加了當(dāng)年的諾貝爾頒獎典禮。

張五?？癜林?/p>

83GraphingDemandCurvesTraditionallyprice(P)isplottedontheverticalaxis&quantitydemanded(Qd)isplottedonthehorizontalaxisTheequationplottedistheinversedemandfunctionP=f(Qd)GraphingDemandCurvesTraditio84GraphingDemandCurvesApointonademandcurveshowseither:MaximumamountofagoodthatwillbepurchasedforagivenpriceMaximumpriceconsumerswillpayforaspecificamountofthegoodGraphingDemandCurvesApoint85GraphingDemandCurvesChangeinquantitydemandedOccurswhenpricechangesMovementalongdemandcurveChangeindemandOccurswhenoneoftheothervariables,ordeterminantsofdemand,changesDemandcurveshiftsrightward

orleftwardGraphingDemandCurvesChangei86ShiftsinDemand

(Figure2.2)Qd01,100700100QuantityPrice(dollars)900P3005001,5001,3001020304050607080D0D1D2??$50,300$50,600??$40,200$40,500DemandincreaseDemanddecreaseShiftsinDemand(Figure87SupplyQuantitysupplied(Qs)AmountofagoodorserviceofferedforsaleduringagivenperiodoftimeSupplyQuantitysupplied(Qs)88SupplySixvariablesthatinfluenceQsPriceofgoodorservice(P)Inputprices(PI)Pricesofgoodsrelatedinproduction(Pr)Technologicaladvances(T)Expectedfuturepriceofproduct(Pe)Numberoffirmsproducingproduct(F)Generalizedsupplyfunction

SupplySixvariablesthatinflu89GeneralizedSupplyFunctionk,l,m,n,r,&sareslopeparametersMeasureeffectonQs

ofchangingoneofthevariableswhileholdingtheothersconstantSignofparametershowshowvariableisrelatedtoQsPositivesignindicatesdirectrelationshipNegativesignindicatesinverserelationshipGeneralizedSupplyFunction90GeneralizedSupplyFunctionVariableRelationtoQsSignofSlopeParameterPPeFPIPrDirectDirectDirectInverseInverseInverseforsubstitutesk=Qs/Pispositivel=Qs/PI

isnegativem=Qs/Pr

isnegativem=Qs/Pr

ispositiver=Qs/Pe

isnegatives=Qs/F

ispositiveDirectforcomplementsn=Qs/T

ispositiveTGeneralizedSupplyFunctionVar91SupplyFunctionSupplyfunction,orsupply,showsrelationbetweenP&Qs

whenallothervariablesareheldconstant

Qs=g(P)SupplyFunctionSupplyfunction92GraphingSupplyCurvesApointonasupplycurveshowseither:MaximumamountofagoodthatwillbeofferedforsaleatagivenpriceMinimumpricenecessarytoinduceproducerstovoluntarilyofferaparticularquantityforsaleGraphingSupplyCurvesApoint93GraphingSupplyCurvesChangeinquantitysuppliedOccurswhenpricechangesMovementalongsupplycurveChangeinsupplyOccurswhenoneoftheothervariables,ordeterminantsofsupply,changesSupplycurveshiftsrightwardorleftwardGraphingSupplyCurvesChangei94S0S2S1SupplydecreaseQs07001009003005001020304050607080ShiftsinSupply

(Figure2.4)QuantityPrice(dollars)P$60,700$60,400????$40,500$40,650SupplyincreaseS0S2S1SupplydecreaseQ95MarketEquilibriumEquilibriumprice&quantityaredeterminedbytheintersectionofdemand&supplycurvesAtthepointofintersection,Qd=QsConsumerscanpurchasealltheywant&producerscansellalltheywantatthe“market-clearing”priceMarketEquilibriumEquilibrium96S0MarketEquilibrium

(Figure2.5)Qd,Qs01,100700100QuantityPrice(dollars)900P3005001,5001,3001020304050607080D0?????S0MarketEquilibrium(Figur97ThemarketforlobstersThemarketforlobstersinZhengzhou,onJanuary20,2009.ThemarketforlobstersThemar98MarketEquilibriumQuantityandPriceEquilibriumoccursattheprice-quantitypairforwhichbothbuyersandsellersaresatisfied.Atthemarketequilibriumpriceof$6perlobster,buyersandsellersareeachabletobuyorsellasmanylobstersastheywishto.MarketEquilibriumQuantityan99D2D1S0DemandShifts(SupplyConstant)

(Figure2.6)Qd,Qs01,100700100QuantityPrice(dollars)900P3005001,5001,3001020304050607080D0???A?B?CD2D1S0DemandShifts(SupplyCo100DemandShiftsDemandShifts101S2S1S0SupplyShifts(DemandConstant)

(Figure2.7)Qd,Qs01,100700100QuantityPrice(dollars)900P3005001,3001020304050607080D0???R?S?TS2S1S0SupplyShifts(DemandCo102SimultaneousShiftsWhendemand&supplyshiftsimultaneouslyCanpredicteitherthedirectioninwhichpricechangesorthedirectioninwhichquantitychanges,butnotboth

Thechangeinequilibriumpriceorquantityissaidtobeindeterminatewhenthedirectionofchangedependsontherelativemagnitudesbywhichdemand&supplyshiftSimultaneousShiftsWhendemand103AChangeinSupplyAChangeinSupply104SD’S’’S’DSimultaneousShifts:

(D,S)QPricemayriseorfall;QuantityrisesP?AQPB?P’Q’Q’’C?P’’SD’S’’S’DSimultaneousShifts:105DSimultaneousShifts:

(D,S)SD’S’’S’QPricefalls;QuantitymayriseorfallP?AQPB?P’Q’Q’’C?P’’DSimultaneousShifts:(D,S)106S’’SimultaneousShifts:

(D,S)DSD’S’QPricerises;QuantitymayriseorfallP?AQPB?P’Q’Q’’C?P’’S’’SimultaneousShifts:(D,107SimultaneousShifts:

(D,S)S’’DSD’S’QPricemayriseorfall;QuantityfallsP?AQPB?P’Q’Q’’C?P’’SimultaneousShifts:(D,S)S108管理經(jīng)濟(jì)學(xué)課件3109Ceiling&FloorPricesQxQuantityPrice(dollars)QxPxPxQuantityPrice(dollars)SxDx2501622233284PanelA–CeilingpriceSxDx250PanelB–FloorpriceCeiling&FloorPricesQxQuant110Excesssupply(FloorPrices)A

situationinwhichpriceexceedsitsequilibriumvalueiscalledoneofexcesssupply,or

surplus.At$8,thereisanexcesssupplyof2000lobstersinthismarket.Excesssupply(FloorPrices)A111ExcessDemandAsituationinwhichpriceliesbelowitsequilibriumvalueisreferredtoasoneofexcessdemand.Atapriceof$4inthislobstermarket,thereisanexcessdemandof2000lobsters.ExcessDemandAsituationinwh112ZeroexcesssupplyanddemandEquilibriumoccursattheprice-quantitypairforwhichbothbuyersandsellersare