曼昆經(jīng)濟(jì)學(xué)原理第四章

2

SUPPLYANDDEMANDI:HOWMARKETSWORK供給與需求（I）：市場如何運(yùn)行TheMarketForcesofSupplyandDemand

供給與需求的市場力量Chapter4TheMarketForcesofSupplyandDemandSupply

and

demand

arethetwowordsthateconomistsusemostoften.Supply

and

demand

aretheforcesthatmakemarketeconomieswork.Modernmicroeconomicsisaboutsupply,demand,andmarketequilibrium.供給與需求的市場力量供給和需求是經(jīng)濟(jì)學(xué)家最常用的兩個詞。供給和需求是讓市場經(jīng)濟(jì)運(yùn)行的力量?，F(xiàn)代微觀經(jīng)濟(jì)學(xué)就是關(guān)于供給、需求和市場均衡的學(xué)科。Markets

Amarketisagroupofbuyersandsellersofaparticulargoodorservice.Thetermssupplyanddemandrefertothebehaviorofpeople...astheyinteractwithoneanotherinmarkets.市場

市場是指某種物品或勞務(wù)的一群買者與賣者的集合。

供給與需求這兩個術(shù)語是指人們在市場上相互交易時(shí)的行為。Marketsandcompetition

市場與競爭

Buyers

determine

demand.買者決定需求

Sellers

determine

supply.賣者決定供給ACompetitiveMarket競爭市場Acompetitivemarketisamarketinwhichtherearemanybuyersandsellerssothateachhasanegligibleimpactonthemarketprice

競爭市場——有很多買者和賣者的市場，所以每一個買者或賣者對市場價(jià)格的影響都可以忽略不計(jì)。Competition:PerfectandOtherwiseProductsarethesameNumerousbuyersandsellerssothateachhasnoinfluenceoverpriceBuyersandSellersarepricetakersPerfectCompetition競爭:完全及其它產(chǎn)品是完全相同的。買者和賣者如此之多，以至于沒有一個買者或賣者可以影響價(jià)格。買者和賣者都是價(jià)格接受者。完全競爭Competition:PerfectandOtherwiseMonopolyOneseller,andsellercontrolspriceOligopolyFewsellersNotalwaysaggressivecompetition競爭:完全及其它壟斷一個賣者，賣者決定價(jià)格。寡頭少數(shù)幾個賣者。并不總是主動地進(jìn)行競爭。Competition:PerfectandOtherwiseMonopolisticCompetitionManysellersSlightlydifferentiatedproductsEachsellermaysetpriceforitsownproduct競爭:完全及其它壟斷競爭許多賣者略有差異的產(chǎn)品每個賣者都有決定自己產(chǎn)品價(jià)格的能力Demand需求Quantitydemanded

istheamount

ofagoodthatbuyersarewillingandabletopurchase.

需求量是指買者愿意而且能夠購買的一種物品或勞務(wù)的數(shù)量。LawofDemand需求規(guī)律Thelawofdemandstatesthatthereisaninverserelationshipbetweenpriceandquantitydemanded.

需求規(guī)律認(rèn)為，價(jià)格與需求量之間的關(guān)系是負(fù)關(guān)系。DemandSchedule需求表Thedemandscheduleisatablethatshowstherelationshipbetweenthe

price

ofthegoodandthe

quantity

demanded.

需求表

——

表示一種物品的價(jià)格與需求量之間關(guān)系的表格。Catherine’sDemandSchedule凱瑟琳的需求表DemandCurve需求曲線The

demandcurve

is

thedownward-slopinglinerelatingpricetoquantitydemanded.需求曲線——把價(jià)格與需求量聯(lián)系在一起的向右下方傾斜的曲線。Figure1Catherine’sDemandSchedule

andDemandCurvePriceofIce-CreamCone02.502.001.501.000.501234567891011QuantityofIce-CreamCones$3.00121.Adecreaseinprice...2....increasesquantityofconesdemanded.圖1.Catherine的需求表和需求曲線冰激凌蛋卷的價(jià)格02.502.001.501.000.501234567891011冰激凌蛋卷需求量$3.00121.價(jià)格下降…

2....蛋卷的需求量上升。MarketDemandversusIndividualDemandMarketdemandreferstothesumofallindividualdemandsforaparticulargoodorservice.Graphically,individualdemandcurvesaresummedhorizontallytoobtainthemarketdemandcurve.市場需求市場需求是指所有個人對某種物品或勞務(wù)需求的總和。從圖形上看,把個人需求曲線水平相加，就得出了市場需求曲線。ChangeinQuantityDemandedversusChangeinDemandChangein

QuantityDemandedMovementalongthedemandcurve.Causedbyachangeinthepriceof theproduct.需求量的變化與需求的變化需求量的變化沿著需求曲線移動。是由于產(chǎn)品價(jià)格變動引起的。0DPriceofIce-Cream

ConesQuantityofIce-CreamConesAtaxthatraisesthepriceofice-creamconesresultsinamovementalongthedemandcurve.AB81.00$2.004ChangesinQuantityDemanded0D冰激凌蛋卷的價(jià)格冰激凌蛋卷的消費(fèi)量提高冰激凌蛋卷價(jià)格的稅收引起沿著需求曲線的移動AB81.00$2.004需求量的變化ShiftsintheDemandCurveConsumerincomePricesofrelatedgoodsTastesExpectationsNumberofbuyers需求曲線的移動消費(fèi)者收入相關(guān)產(chǎn)品價(jià)格嗜好預(yù)期買者數(shù)量ShiftsintheDemandCurveChangeinDemandAshiftinthedemandcurve,either totheleftorright.Causedbyachangeina determinantotherthantheprice.需求曲線的移動需求的變化需求曲線的移動，向左或者向右。是由價(jià)格以外的因素變化引起的。ShiftsintheDemandCurve0D1PriceofIce-CreamConeQuantityofIce-CreamConesD3D2IncreaseindemandDecreaseindemand需求曲線的移動0D1冰激凌蛋卷的價(jià)格冰激凌蛋卷的數(shù)量D3D2需求增加需求減少ConsumerIncome消費(fèi)者收入Asincomeincreasesthedemandforanormalgoodwillincrease.

收入增加，正常商品的需求增加Asincomeincreasesthedemandforaninferiorgoodwilldecrease.

收入增加，劣等品的需求減少ConsumerIncome

NormalGood$3.002.502.001.501.000.50213456789101211PriceofIce-CreamConeQuantityofIce-CreamCones0IncreaseindemandAnincreaseinincome...D1D2消費(fèi)者收入正常商品$3.002.502.001.501.000.50213456789101211冰激凌蛋卷的價(jià)格冰激凌蛋卷的數(shù)量0需求增加收入增加...D1D2ConsumerIncome

InferiorGood$3.002.502.001.501.000.50213456789101211PriceofIce-CreamConeQuantityofIce-CreamCones0DecreaseindemandAnincreaseinincome...D1D2消費(fèi)者收入劣等品$3.002.502.001.501.000.50213456789101211冰激凌蛋卷的價(jià)格冰激凌蛋卷的數(shù)量0需求減少收入增加...D1D2PricesofRelatedGoods

Substitutes&ComplementsWhenafallinthepriceofonegoodreduces

thedemandforanothergood,thetwogoodsarecalledsubstitutes.Whenafallinthepriceofonegoodincreases

thedemandforanothergood,thetwogoodsarecalledcomplements.相關(guān)物品的價(jià)格

替代品和互補(bǔ)品當(dāng)一種物品價(jià)格下降減少了另一種物品需求時(shí)，這兩種物品被稱為替代品。當(dāng)一種物品價(jià)格下降增加了另一種物品需求時(shí)，這兩種物品被稱為互補(bǔ)品。Table1VariablesThatInfluenceBuyersCopyright?2004South-Western表1.影響買者的變量變量這些變量的變動將...價(jià)格表現(xiàn)為沿著需求曲線的變動收入移動需求曲線相關(guān)物品價(jià)格移動需求曲線嗜好移動需求曲線預(yù)期移動需求曲線買者數(shù)量移動需求曲線Supply供給Quantitysupplied

istheamountofagoodthatsellersarewillingandabletosell.

供給量是指賣者愿意而且能夠出售的一種物品或勞務(wù)的數(shù)量。LawofSupply供給規(guī)律The

lawofsupply

statesthatthereisadirect(positive)relationshipbetweenpriceandquantity

supplied.供給規(guī)律認(rèn)為，價(jià)格與供給量之間的關(guān)系是正關(guān)系。SupplySchedule供給表The

supplyschedule

is

atablethatshowstherelationshipbetweenthepriceofthegoodandthequantitysupplied.供給表是表示一種物品價(jià)格與供給量之間關(guān)系的表格。

Ben’sSupplySchedule供給表SupplyCurve供給曲線The

supplycurve

istheupward-slopinglinerelatingpricetoquantitysupplied.

供給曲線——把價(jià)格與供給量聯(lián)系在一起的向右上方傾斜的曲線。Figure5Ben’sSupplySchedule

andSupplyCurvericeofIce-CreamCone02.502.001.501.001234567891011QuantityofIce-CreamCones$3.00120.501.Anincrease

inprice...2....

increasesquantityofconessupplied.圖5.Ben供給表與供給曲線冰激凌蛋卷需求量02.502.001.501.001234567891011冰激凌蛋卷的供給量$3.00120.501.價(jià)格上升…

2....供給量增加。MarketSupplyversusIndividualSupplyMarketsupplyreferstothesumofallindividualsuppliesforallsellersofaparticulargoodorservice.Graphically,individualsupplycurvesaresummedhorizontallytoobtainthemarketsupplycurve.市場供給市場供給是指某種物品或勞務(wù)的所有賣者個人供給的總和。從圖形上看,把個人供給曲線水平相加，就得出了市場供給曲線。ShiftsintheSupplyCurveInputpricesTechnologyExpectationsNumberofproducers供給曲線的移動投入要素價(jià)格技術(shù)預(yù)期生產(chǎn)者數(shù)量ChangeinQuantitySuppliedversusChangeinSupplyChangeinQuantitySuppliedMovementalongthesupplycurve.Causedbyachangeinthemarketpriceoftheproduct.供給量的變化與供給的變化供給量的變化沿著供給曲線移動。是由于產(chǎn)品的市場價(jià)格變動引起的。ChangeinQuantitySupplied15PriceofIce-CreamConeQuantityofIce-CreamCones0S1.00AC$3.00Ariseinthepriceoficecreamconesresultsinamovementalongthesupplycurve.供給量的變化15冰激凌蛋卷的價(jià)格冰激凌蛋卷的數(shù)量0S1.00AC$3.00冰激凌蛋卷的市場價(jià)格上升導(dǎo)致供給量沿著供給曲線的移動。ShiftsintheSupplyCurveChangeinSupplyAshiftinthesupplycurve,eithertotheleftorright.

Causedbyachangeinadeterminantotherthanprice.供給曲線的移動供給的變化供給曲線的移動，向左或者向右。

是由于價(jià)格以外的因素變化造成的。Shifts

intheSupplyCurvePriceofIce-CreamConeQuantityofIce-CreamCones0S1S2S3IncreaseinSupplyDecreaseinSupply供給曲線的移動冰激凌蛋卷的價(jià)格冰激凌蛋卷的數(shù)量0S1S2S3供給增加供給減少Table2VariablesThatInfluenceSellers供給量的變化與供給的變化SUPPLYANDDEMANDTOGETHER

供給與需求的結(jié)合Equilibrium

referstoasituationinwhichthepricehasreachedthelevelwherequantitysuppliedequalsquantitydemanded.

市場均衡——

價(jià)格水平達(dá)到供給量與需求量相等的狀態(tài)。SupplyandDemandTogetherEquilibriumPriceThepricethatbalancessupplyanddemand.Onagraph,itisthepriceatwhichthesupplyanddemandcurvesintersect.EquilibriumQuantityThequantitythatbalancessupplyanddemand.Onagraphitisthequantityatwhichthesupplyanddemandcurvesintersect.

供給與需求的結(jié)合均衡價(jià)格使供給與需求平衡的價(jià)格。從圖形上看，就是供給曲線與需求曲線相交時(shí)的價(jià)格。均衡數(shù)量當(dāng)價(jià)格調(diào)整到使供給與需求平衡時(shí)的供給量與需求量。從圖形上看，就是供給曲線與需求曲線相交時(shí)的數(shù)量。

SupplyandDemandTogetherDemandScheduleSupplyScheduleAt$2.00,thequantitydemandedisequaltothequantitysupplied!供給與需求的結(jié)合需求表供給表在$2.00時(shí),需求量等于供給量!Figure8TheEquilibriumofSupply

andDemandCopyright?2003Southwestern/ThomsonLearningPriceofIce-CreamCone0123456789101112QuantityofIce-CreamCones13EquilibriumquantityEquilibriumpriceEquilibriumSupplyDemand$2.00表8.供給與需求的均衡冰激凌蛋卷需求量0123456789101112冰激凌蛋卷的數(shù)量13均衡數(shù)量均衡價(jià)格均衡供給需求$2.00Figure9MarketsNotinEquilibriumPriceofIce-CreamCone0SupplyDemand(a)ExcessSupplyQuantitydemandedQuantitysuppliedSurplusQuantityofIce-CreamCones4$2.50102.007圖9.非均衡狀態(tài)的市場冰激凌蛋卷需求量0供給需求(a)超額供給需求量供給量過剩冰激凌蛋卷的數(shù)量4$2.50102.007EquilibriumSurplusWhenprice>equilibriumprice,thenquantitysupplied>quantitydemanded.Thereisexcesssupplyorasurplus.Supplierswilllowerthepricetoincreasesales,therebymovingtowardequilibrium.均衡過剩當(dāng)價(jià)格高于均衡價(jià)格時(shí)，供給量大于需求量。

存在超額供給或過剩。

供給者通過降低價(jià)格來增加銷售，這使價(jià)格向其均衡水平變動。EquilibriumShortageWhenprice<equilibriumprice,thenquantitydemanded>thequantitysupplied.

Thereisexcessdemandorashortage.Supplierswillraisethepriceduetotoomanybuyerschasingtoofewgoods,therebymovingtowardequilibrium.均衡短缺當(dāng)價(jià)格低于市場均衡價(jià)格時(shí)，需求量超過了供給量。

存在著超額需求或短缺。

由于太多賣者要購買太少的物品，供給者將提高價(jià)格。因此價(jià)格將趨向于市場均衡價(jià)格。Figure9MarketsNotinEquilibriumPriceofIce-CreamCone0QuantityofIce-CreamConesSupplyDemand(b)ExcessDemandQuantitysuppliedQuantitydemanded1.5010$2.0074Shortage圖9.非均衡狀態(tài)的市場冰激凌蛋卷需求量0冰激凌蛋卷的數(shù)量供給供給(b)超額需求供給量需求量1.5010$2.0074短缺Equilibrium

均衡Lawofsupplyanddemand

需求規(guī)律Theclaimthatthepriceofanygoodadjuststobringthequantitysuppliedandthequantitydemandedforthatgoodintobalance.認(rèn)為任何一種物品價(jià)格的調(diào)整都會使該物品供求平衡的觀點(diǎn)。ThreeStepsToAnalyzingChangesinEquilibriumDecidewhethertheeventshiftsthesupplyordemandcurve(orboth).Decidewhetherthecurve(s)shift(s)totheleftortotheright.Usethesupply-and-demanddiagramtoseehowtheshiftaffectsequilibriumpriceandquantity.分析均衡的三個步驟確定該事件是使供給曲線移動，還是使需求曲線移動，或者使兩種曲線都移動。確定曲線是向右移動，還是向左移動。用供求圖來考察這種移動如何影響均衡價(jià)格和數(shù)量。HowanIncreaseinDemandAffectstheEquilibriumPriceofIce-CreamCone2.0007QuantityofIce-CreamConesSupplyInitialequilibriumD11.Hotweatherincreasesthedemandforicecream...D22....resultinginahigherprice...$2.50103....andahigherquantitysold.Newequilibrium需求增加如何影響均衡冰激凌蛋卷的價(jià)格2.0007冰激凌蛋卷的數(shù)量供給原來的均衡D11.天氣熱使冰激凌需求增加...D22.…引起價(jià)格上升...$2.50103.…及銷售量更多。新均衡ThreeStepstoAnalyzingChangesinEquilibrium

ShiftsinCurvesversusMovementsalongCurvesAshiftinthesupplycurveiscalledachangeinsupply.Amovementalongafixedsupplycurveiscalledachangeinquantitysupplied.Ashiftinthedemandcurveiscalledachangeindemand.Amovementalongafixeddemandcurveiscalledachangeinquantitydemanded.分析均衡的三個步驟曲線移動與沿著曲線的移動:供給曲線的移動被稱為供給的變化。沿著固定的供給曲線的移動被稱為供給量的變化。需求曲線的移動被稱為需求的變化。沿著固定的需求曲線的移動被稱為需求量的變化。S2HowaDecreaseinSupplyAffectstheEquilibriumPriceofIce-CreamCone2.00012347891112QuantityofIce-CreamCones13DemandInitialequilibriumS1101.Anearthquakereducesthesupplyoficecream...Newequilibrium2....resultinginahigherprice...$2.503....andalowerquantitysold.S2供給減少如何影響均衡冰激凌蛋卷的價(jià)格2.00012347891112冰激凌蛋卷的數(shù)量13需求原來的均衡S110地震減少了冰激凌的供給...新均衡2.…引起價(jià)格上升...$2.503.…以及銷售量減少。WhatHappenstoPriceandQuantityWhenSupplyorDemandShifts?當(dāng)供給或需求變動時(shí)，價(jià)格和數(shù)量

會發(fā)生什么變化?SummaryEconomistsusethemodelofsupplyanddemandtoanalyzecompetitivemarkets.Inacompetitivemarket,therearemanybuyersandsellers,eachofwhomhaslittleornoinfluenceonthemarketprice.小結(jié)經(jīng)濟(jì)學(xué)家用供求模型來分析競爭市場。在競爭市場中，有許多買者和賣者，他們當(dāng)中的任何一個對市場價(jià)格具有極小或者沒有影響力。SummaryThedemandcurveshowshowthequantityofagooddependsupontheprice.Accordingtothelawofdemand,asthepriceofagoodfalls,thequantitydemandedrises.Therefore,thedemandcurveslopesdownward.Inadditiontoprice,otherdeterminantsofhowmuchconsumerswanttobuyincludeincome,thepricesofcomplementsandsubstitutes,tastes,expectations,andthenumberofbuyers.Ifo