曼昆经济学原理-Chap-04PPT课件

TheMarketForcesofSupplyandDemandChapter4Copyright©2001byHarcourt,Inc.Allrightsreserved.  Requestsforpermissiontomakecopiesofanypartoftheworkshouldbemailedto:PermissionsDepartment,HarcourtCollegePublishers,6277SeaHarborDrive,Orlando,Florida32887-6777.LEARNINGOBJECTIVES:Bytheendofthischapter,studentsshouldunderstand:whatacompetitivemarketis.whatdeterminesthedemandforagoodinacompetitivemarket.whatdeterminesthesupplyofagoodinacompetitivemarket.howsupplyanddemandtogethersetthepriceofagoodandthequantitysold.thekeyroleofpricesinallocatingscarceresourcesinmarketeconomies.TheMarketForcesofSupplyandDemandSupplyanddemandarethetwowordsthateconomistsusemostoften.Supplyanddemandaretheforcesthatmakemarketeconomieswork.Modernmicroeconomicsisaboutsupply,demand,andmarketequilibrium.MarketsAmarketisagroupofbuyersandsellersofaparticulargoodorservice.Thetermssupplyanddemandrefertothebehaviorofpeople...astheyinteractwithoneanotherinmarkets.MarketsBuyersdeterminedemand.Sellersdeterminesupply.MarketType:ACompetitiveMarketAcompetitivemarketisamarket...withmanybuyersandsellers.thatisnotcontrolledbyanyoneperson.inwhichanarrowrangeofpricesareestablishedthatbuyersandsellersactupon.Competition:PerfectandOtherwiseProductsarethesameNumerousbuyersandsellerssothateachhasnoinfluenceoverpriceBuyersandSellersarepricetakersTherearenobarrierstoenterorexitthemarket(buyersandsellercanfreelyenterorexitthemarket.)PerfectCompetitionCompetition:PerfectandOtherwiseMonopolyOneseller,andsellercontrolspriceOligopolyFewsellersNotalwaysaggressivecompetitionCompetition:PerfectandOtherwiseMonopolisticCompetitionManysellersSlightlydifferentiatedproductsEachsellermaysetpriceforitsownproductDemandQuantitydemandedistheamountofagoodthatbuyersarewillingandabletopurchase.LawofDemand(需求定律/需求律)Thelawofdemandstatesthatthereisaninverserelationshipbetweenpriceandquantitydemanded.DemandScheduleThedemandscheduleisatablethatshowstherelationshipbetweenthepriceofthegoodandthequantitydemanded.DemandScheduleDemandCurveThedemandcurveisthedownward-slopinglinerelatingpricetoquantitydemanded.DemandCurve$3.002.502.001.501.000.50213456789101211PriceofIce-CreamConeQuantityofIce-CreamCones0CeterisParibusCeterisparibusisaLatinphrasethatmeansallvariablesotherthantheonesbeingstudiedareassumedtobeconstant.Literally,ceterisparibusmeans“otherthingsbeingequal.”Thedemandcurveslopesdownwardbecause,ceterisparibus,lowerpricesimplyagreaterquantitydemanded!MarketDemandMarketdemandreferstothesumofallindividualdemandsforaparticulargoodorservice.Graphically,individualdemandcurvesaresummedhorizontallytoobtainthemarketdemandcurve.ChangeinQuantityDemandedversusChangeinDemandChangeinQuantityDemandedMovementalongthedemandcurve.Causedbyachangeinthepriceoftheproduct.ChangesinQuantityDemanded0D1PriceofCigarettesperPackNumberofCigarettesSmokedperDayAtaxthatraisesthepriceofcigarettesresultsinamovementalongthedemandcurve.AC202.00$4.0012ChangeinQuantityDemandedversusChangeinDemandChangeinDemandAshiftinthedemandcurve,eithertotheleftorright.Causedbyachangeinadeterminantotherthantheprice.ChangesinDemand0D1PriceofIce-CreamConeQuantityofIce-CreamConesD3D2IncreaseindemandDecreaseindemandQ3Q1Q2DeterminantsofDemandMarketpriceConsumerincomePricesofrelatedgoodsTastesExpectationsNumberofbuyersConsumerIncomeAsincomeincreasesthedemandforanormalgoodwillincrease.Asincomeincreasesthedemandforaninferiorgoodwilldecrease.ConsumerIncomeNormalGood$3.002.502.001.501.000.50213456789101211PriceofIce-CreamConeQuantityofIce-CreamCones0IncreaseindemandAnincreaseinincome...D1D2ConsumerIncomeInferiorGood$3.002.502.001.501.000.50213456789101211PriceofIce-CreamConeQuantityofIce-CreamCones0DecreaseindemandAnincreaseinincome...D1D2PricesofRelatedGoodsSubstitutes&ComplementsWhenafallinthepriceofonegoodreducesthedemandforanothergood,thetwogoodsarecalledsubstitutes.Whenafallinthepriceofonegoodincreasesthedemandforanothergood,thetwogoodsarecalledcomplements.ChangeinQuantityDemandedversusChangeinDemandVariablesthatAffectQuantityDemandedAChangeinThisVariable...PriceRepresentsamovementalongthedemandcurveIncomeShiftsthedemandcurvePricesofrelatedgoodsShiftsthedemandcurveTastesShiftsthedemandcurveExpectationsShiftsthedemandcurveNumberofbuyersShiftsthedemandcurveGeneralDemandFunctionSixvariablesthatinfluenceQdPriceofgoodorservice(P)Incomesofconsumers(M)Pricesofrelatedgoods&services(PR)Expectedfuturepriceofproduct(Pe)Numberofconsumersinmarket(N)GeneraldemandfunctionGeneralDemandFunctionb,c,d,e,f,&gareslopeparametersMeasureeffectonQdofchangingoneofthevariableswhileholdingtheothersconstantSignofparametershowshowvariableisrelatedtoQdPositivesignindicatesdirectrelationshipNegativesignindicatesinverserelationshipGeneralDemandFunctionVariableRelationtoQdSignofSlopeParameterPPeNMPRInverseDirectDirectDirectDirectfornormalgoodsInverseforinferiorgoodsDirectforsubstitutesb=Qd/Pisnegativec=Qd/Mispositivec=Qd/Misnegatived=Qd/PRispositived=Qd/PRisnegativef=Qd/Peispositiveg=Qd/NispositiveInverseforcomplementse=Qd/ispositiveDirectDemandFunctionThedirectdemandfunction,orsimplydemand,showshowquantitydemanded,Qd,isrelatedtoproductprice,P,whenallothervariablesareheldconstantQd=f(P)LawofDemandQdincreaseswhenPfalls&QddecreaseswhenPrises,allelseconstantQd/PmustbenegativeInverseDemandFunction(逆需求函数)Traditionally,price(P)isplottedontheverticalaxis&quantitysupplied(Qd)isplottedonthehorizontalaxisTheequationplottedistheinversedemandfunction,P=f(Qd)P/QdmustbenegativeSupplyQuantitysuppliedistheamountofagoodthatsellersarewillingandabletosell.LawofSupplyThelawofsupplystatesthatthereisadirect(positive)relationshipbetweenpriceandquantitysupplied.DeterminantsofSupplyMarketpriceInputpricesTechnologyPricesofrelatedgoodsExpectationsNumberofproducersSupplyScheduleThesupplyscheduleisatablethatshowstherelationshipbetweenthepriceofthegoodandthequantitysupplied.SupplyScheduleSupplyCurveThesupplycurveistheupward-slopinglinerelatingpricetoquantitysupplied.SupplyCurve$3.002.502.001.501.000.50213456789101211PriceofIce-CreamConeQuantityofIce-CreamCones0MarketSupplyMarketsupplyreferstothesumofallindividualsuppliesforallsellersofaparticulargoodorservice.Graphically,individualsupplycurvesaresummedhorizontallytoobtainthemarketsupplycurve.DeterminantsofSupplyMarketpriceInputpricesTechnologyPricesofrelatedgoodsExpectationsNumberofproducersChangeinQuantitySuppliedversusChangeinSupplyChangeinQuantitySuppliedMovementalongthesupplycurve.Causedbyachangeinthemarketpriceoftheproduct.ChangeinQuantitySupplied15PriceofIce-CreamConeQuantityofIce-CreamCones0S1.00AC$3.00Ariseinthepriceoficecreamconesresultsinamovementalongthesupplycurve.ChangeinQuantitySuppliedversusChangeinSupplyChangeinSupplyAshiftinthesupplycurve,eithertotheleftorright.Causedbyachangeinadeterminantotherthanprice.ChangeinSupplyPriceofIce-CreamConeQuantityofIce-CreamCones0S1S2S3IncreaseinSupplyDecreaseinSupplyChangeinQuantitySuppliedversusChangeinSupplySupplySixvariablesthatinfluenceQsPriceofgoodorservice(P)Inputprices(PI)Pricesofgoodsrelatedinproduction(Pr)Technologicaladvances(T)Expectedfuturepriceofproduct(Pe)Numberoffirmsproducingproduct(F)GeneralsupplyfunctionGeneralSupplyFunctionk,l,m,n,r,&sareslopeparametersMeasureeffectonQsofchangingoneofthevariableswhileholdingtheothersconstantSignofparametershowshowvariableisrelatedtoQsPositivesignindicatesdirectrelationshipNegativesignindicatesinverserelationshipGeneralSupplyFunctionVariableRelationtoQsSignofSlopeParameterPPeFPIPrDirectDirectDirectInverseInverseInverseforsubstitutesk=Qs/Pispositivel=Qs/PIisnegativem=Qs/Prisnegativem=Qs/Prispositiver=Qs/Peisnegatives=Qs/FispositiveDirectforcomplementsn=Qs/TispositiveTDirectSupplyFunctionThedirectsupplyfunction,orsimplysupply,showshowquantitysupplied,Qs,isrelatedtoproductprice,P,whenallothervariablesareheldconstantQs=f(P)InverseSupplyFunction(逆供给函数)Traditionally,price(P)isplottedontheverticalaxis&quantitysupplied(Qs)isplottedonthehorizontalaxisTheequationplottedistheinversesupplyfunction,P=f(Qs)ALTERNATIVECLASSROOMEXAMPLE:Gothroughtheseexamplesofeventswhichwouldshifteitherthedemandorsupplyof#2leadpencils:anincreaseintheincomeofconsumersanincreaseintheuseofstandardizedexams(usingopscanforms)adecreaseinthepriceofgraphite(usedintheproductionofpencils)adecreaseinthepriceofinkpensthestartofaschoolyearnewtechnologythatlowersthecostofproducingpencilsSupplyandDemandTogetherEquilibriumPrice（市场均衡价格）（market-clearingprice，市场出清价格）Thepricethatbalancessupplyanddemand.Onagraph,itisthepriceatwhichthesupplyanddemandcurvesintersect.EquilibriumQuantity（市场均衡数量）Thequantitythatbalancessupplyanddemand.Onagraphitisthequantityatwhichthesupplyanddemandcurvesintersect.SupplyandDemandTogetherDemandScheduleSupplyScheduleAt$2.00,thequantitydemandedisequaltothequantitysupplied!SupplyDemandPriceofIce-CreamConeQuantityofIce-CreamConesEquilibriumofSupplyandDemand2134567891012110$3.002.502.001.501.000.50EquilibriumPriceofIce-CreamConeQuantityofIce-CreamCones2134567891012110$3.002.502.001.501.000.50SupplyDemandSurplusExcessSupplySurplusWhenthepriceisabovetheequilibriumprice,thequantitysuppliedexceedsthequantitydemanded.Thereisexcesssupplyorasurplus.Supplierswilllowerthepricetoincreasesales,therebymovingtowardequilibrium.ExcessDemandQuantityofIce-CreamConesPriceofIce-CreamCone$2.00012345678910111213SupplyDemand$1.50ShortageShortageWhenthepriceisbelowtheequilibriumprice,thequantitydemandedexceedsthequantitysupplied.Thereisexcessdemandorashortage.Supplierswillraisethepriceduetotoomanybuyerschasingtoofewgoods,therebymovingtowardequilibrium.ThreeStepsToAnalyzingChangesinEquilibriumDecidewhethertheeventshiftsthesupplyordemandcurve(orboth).Decidewhetherthecurve(s)shift(s)totheleftortotheright.Examinehowtheshiftaffectsequilibriumpriceandquantity.HowanIncreaseinDemandAffectstheEquilibriumPriceofIce-CreamCone2.0007QuantityofIce-CreamConesSupplyInitialequilibriumD11.Hotweatherincreasesthedemandforicecream...D22....resultinginahigherprice...$2.50103....andahigherquantitysold.NewequilibriumHarcourt,Inc.itemsandderiveditemscopyright©2001byHarcourt,Inc.ShiftsinCurvesversusMovementsalongCurvesAshiftinthesupplycurveiscalledachangeinsupply.Amovementalongafixedsupplycurveiscalledachangeinquantitysupplied.Ashiftinthedemandcurveiscalledachangeindemand.Amovementalongafixeddemandcurveiscalledachangeinquantitydemanded.S2HowaDecreaseinSupplyAffectstheEquilibriumPriceofIce-CreamCone2.00012347891112QuantityofIce-CreamCones13DemandInitialequilibriumS1101.Anearthquakereducesthesupplyoficecream...Newequilibrium2....resultinginahigherprice...$2.503....andalowerquantitysold.SimultaneousShiftsofSupplyandDemandaaHoursofDayCarePriceperHourS1990S2001P2001Q2001P1990Q1990D1990D2001ABEquilibriumpriceisambiguousandequilibriumquantityincreases.b.Equilibriumpriceincreasesandequilibriumquantityisambiguous.Equilibriumpriceisambiguousandequilibriumquantitydecreases.Equilibriumpricedecreasesandequilibriumquantityisambiguous.WhatHappenstoPriceandQuantityWhenSupplyorDemandShifts?ExerciseSupposethatthedemandandsupplyfunctionsforgoodXareQd=50－8PQs=-17.5+10Pa.Whataretheequilibriumpriceandquantity?bWhatisthemarketoutcomeifpriceis＄2.75?Whatdoyouexpecttohappen?Explain.c.Whatisthemarketoutcomeifpriceis＄4.25?Whatdoyouexpecttohappen?Explain.d.WhathappensifthedemandfunctionbecomesQd=59－8P?e.WhathappensifthesupplyfunctionbecomesQs=-40+10P?Solutiona.Atequilibrium,PE=＄3.75QE=20.b.WhenP=＄2.75,Qd=28Qs=10;thereisashortageof18units.c.WhenP=＄4.25,Qd=16Qs=25;thereisasurplusof9units.d.Atequilibrium,PE=＄4.25QE=25.e.Atequilibrium,PE=＄5QE=10.ProblemsandApplications9.Quantitysuppliedequalsquantitydemandedatapriceof$6andquantityof81pizzas(Figure4-26).Ifpriceweregreaterthan$6,quantitysuppliedwouldexceedquantitydemanded,sosupplierswouldreducetheirpricetogainsales.Ifpricewerelessthan$6,quantitydemandedwouldexceedquantitysupplied,sosupplierscouldraisetheirpricewithoutlosingsales.Inbothcases,thepricewouldcontinuetoadjustuntilitreached$6,theonlypriceatwhichthere'sneithersurplusnorshortage.ProblemsandApplications10.a.Ifthepriceofflourfalls,sinceflourisaningredientinbagels,thesupplycurveforbagelswouldshifttotheright.Theresult,showninFigure4-27,wouldbeafallinthepriceofbagelsandariseintheequilibriumquantityofbagels.Figure4-27Sincecreamcheeseisacomplementtobagels,theriseinquantitydemandedofbagelsincreasesthedemandforcreamcheese,asshowninFigure4-28.Theresultisariseinboththeequilibriumpriceandquantityofcreamcheese.So,afallinthepriceofflourindeedraisesboththeequilibriumpriceofcreamcheeseandtheequilibriumquantityofbagels.Figure4-28Whathappensifthepriceofmilkfalls?Sincemilkisaningredientincreamcheese,thefallinthepriceofmilkleadstoanincreaseinthesupplyofcreamcheese.Thisleadstoadecreaseinthepriceofcreamcheese(Figure4-29),ratherthanariseinthepriceofcreamcheese.Soafallinthepriceofmilkcouldn'thavebeenresponsibleforthepatternobserved.Figure4-29b.Inpart(a),wefoundthatafallinthepriceofflourledtoariseinthepriceofcreamcheeseandariseintheequilibriumquantityofbagels.Ifthepriceofflourrose,theoppositewouldbetrue;itwouldleadtoafallinthepriceofcreamcheeseandafallintheequilibriumquantityofbagels.Sincethequestionsaystheequilibriumpriceofcreamcheesehasrisen,itcouldn'thavebeencausedbyariseinthepriceofflour.Whathappensifthepriceofmilkrises?Frompart(a),wefoundthatafallinthepriceofmilkcausedadeclineinthepriceofcreamcheese,soariseinthepriceofmilkwouldcauseariseinthepriceofcreamcheese.Sincebagelsandcreamcheesearecomplements,theriseinthepriceofcreamcheesewouldreducethedemandforbagels,asFigure4-30shows.Theresultisadeclineintheequilibriumquantityofbagels.Soariseinthepriceofmilkdoescausebothariseinthepriceofcreamcheeseandadeclineintheequilibriumquantityofbagels.Figure4-3011.a.AsFigure4-31shows,thesupplycurveisvertical.Theconstantsupplymakessensebecausethebasketballarenahasafixednumberofseatsnomatterwhattheprice.b.Quantitysuppliedequalsquantitydemandedatapriceof$8.Theequilibriumquantityis8,000tickets.PriceQuantityDemandedQuantitySupplied$414,0008,000811,0008,000128,0008,000165,0008,000202,0008,000Thenewequilibriumpricewillbe$12,whichequatesquantitydemandedtoquantitysupplied.Theequilibriumquantityis8,000tickets.SummaryEconomistsusethemodelofsupplyanddemandtoanalyzecompetitivemarkets.Thedemandcurveshowshowthequantityofagooddependsupontheprice.SummaryAccordingtothelawofdemand,asthepriceofagoodrises,thequantitydemandedfalls.Inadditiontoprice,otherdeterminantsofquantitydemandedincludeincome,tastes,expectations,andthepricesofcomplementsandsubstitutes.SummaryThesupplycurveshowshowthequantityofagoodsupplieddependsupontheprice.Accordingtothelawofsupply,asthepriceofagoodrises,thequantitysuppliedrises.SummaryInadditiontoprice,otherdeterminantsofquantitysuppliedincludeinputprices,technology,andexpectations.Marketequilibriumisdeterminedbytheintersectionofthesupplyanddemandcurves.SummarySupplyanddemandtogetherdeterminethepricesoftheeconomy’sgoodsandservices.Inmarketeconomies,pricesarethesignalsthatguidetheallocationofresources.GraphicalReviewHowanIncreaseinDemandAffectstheEquilibriumPriceofIce-CreamCone2.000710QuantityofIce-CreamConesSupplyInitialequilibriumD1HowanIncreaseinDemandAffectstheEquilibriumPriceofIce-CreamCone2.000710QuantityofIce-CreamConesSupplyInitialequilibriumD11.Hotweatherincreasesthedemandforicecream...HowanIncreaseinDemandAffectstheEquilibriumPriceofIce-CreamCone2.000710QuantityofIce-CreamConesSupplyInitialequilibriumD11.Hotweatherincreasesthedemandforicecream...D2Newequilibrium$2.50HowanIncreaseinDemandAffectstheEquilibriumPriceofIce-CreamCone2.000710QuantityofIce-CreamConesSupplyInitialequilibriumD11.Hotweatherincreasesthedemandforicecream...D2Newequilibrium2....resultinginahigherprice...$2.50HowanIncreaseinDemandAffectstheEquilibriumPriceofIce-CreamCone2.000710QuantityofIce-CreamConesSupplyInitialequilibriumD11.Hotweatherincreasesthedemandforicecream...D2Newequilibrium2....resultinginahigherprice...$2.503....andahigherquantitysold.Harcourt,Inc.itemsandderiveditemscopyright©2001byHarcourt,Inc.HowanIncreaseinDemandAffectstheEquilibriumPriceofIce-CreamCone2.000710QuantityofIce-CreamConesSupplyInitialequilibriumD11.Hotweatherincreasesthedemandforicecream...D2Newequilibrium2....resultinginahigherprice...$2.503....andahigherquantitysold.Harcourt,Inc.itemsandderiveditemscopyright©2001byHarcourt,Inc.HowaDecreaseinSupplyAffectstheEquilibriumPriceofIce-CreamCone2.0001234567891112QuantityofIce-CreamCones13DemandInitialequilibriumS110HowaDecreaseinSupplyAffectstheEquilibriumPriceofIce-CreamCone2.0001234567891112QuantityofIce-CreamCones13DemandInitialequilibriumS1101.Anearthquakereducesthesupplyoficecream...HowaDecreaseinSupplyAffectstheEquilibriumPriceofIce-CreamCone2.0001234567891112QuantityofIce-CreamCones13DemandInitialequilibriumS1101.Anearthquakereducesthesupplyoficecream...HowaDecreaseinSupplyAffectstheEquilibriumPriceofIce-CreamCone2.0001234567891112QuantityofIce-CreamCones13DemandInitialequilibriumS1101.Anearthquakereducesthesupplyoficecream...Newequilibrium$2.50HowaDecreaseinSupplyAffectstheEquilibriumPriceofIce-CreamCone2.0001234567891112QuantityofIce-CreamCones13DemandInitialequilibriumS1101.Anearthquakereducesthesupplyoficecream...Newequilibrium$2.502....resultinginahigherprice...HowaDecreaseinSupplyAffectstheEquilibriumPriceofIce-CreamCone2.00012347891112QuantityofIce-CreamCones13DemandInitialequilibriumS1101.Anearthquakereducesthesupplyoficecream...Newequilibrium$2.502....resultinginahigherprice...3....andalowerquantitysold.