曼昆哈佛大学经济学原理课件第四章.ppt

,TheMarketForcesofSupplyandDemand,Chapter4,Copyright2001byHarcourt,Inc.Allrightsreserved.Requestsforpermissiontomakecopiesofanypartoftheworkshouldbemailedto:PermissionsDepartment,HarcourtCollegePublishers,6277SeaHarborDrive,Orlando,Florida32887-6777.,TheMarketForcesofSupplyandDemand,Supplyanddemandarethetwowordsthateconomistsusemostoften.Supplyanddemandaretheforcesthatmakemarketeconomieswork.Modernmicroeconomicsisaboutsupply,demand,andmarketequilibrium.,Markets,Amarketisagroupofbuyersandsellersofaparticulargoodorservice.Thetermssupplyanddemandrefertothebehaviorofpeople.astheyinteractwithoneanotherinmarkets.,Markets,Buyersdeterminedemand.,Sellersdeterminesupply.,MarketType:ACompetitiveMarket,Acompetitivemarketisamarket.,withmanybuyersandsellers.,thatisnotcontrolledbyanyoneperson.,inwhichanarrowrangeofpricesareestablishedthatbuyersandsellersactupon.,Competition:PerfectandOtherwise,ProductsarethesameNumerousbuyersandsellerssothateachhasnoinfluenceoverpriceBuyersandSellersarepricetakers,PerfectCompetition,Competition:PerfectandOtherwise,MonopolyOneseller,andsellercontrolspriceOligopolyFewsellersNotalwaysaggressivecompetition,Competition:PerfectandOtherwise,MonopolisticCompetitionManysellersSlightlydifferentiatedproductsEachsellermaysetpriceforitsownproduct,Demand,Quantitydemandedistheamountofagoodthatbuyersarewillingandabletopurchase.,LawofDemand,Thelawofdemandstatesthatthereisaninverserelationshipbetweenpriceandquantitydemanded.,DemandSchedule,Thedemandscheduleisatablethatshowstherelationshipbetweenthepriceofthegoodandthequantitydemanded.,DemandSchedule,DeterminantsofDemand,MarketpriceConsumerincomePricesofrelatedgoodsTastesExpectations,DemandCurve,Thedemandcurveisthedownward-slopinglinerelatingpricetoquantitydemanded.,DemandCurve,$3.00,2.50,2.00,1.50,1.00,0.50,2,1,3,4,5,6,7,8,9,10,12,11,PriceofIce-CreamCone,QuantityofIce-CreamCones,0,CeterisParibus,CeterisparibusisaLatinphrasethatmeansallvariablesotherthantheonesbeingstudiedareassumedtobeconstant.Literally,ceterisparibusmeans“otherthingsbeingequal.”,Thedemandcurveslopesdownwardbecause,ceterisparibus,lowerpricesimplyagreaterquantitydemanded!,MarketDemand,Marketdemandreferstothesumofallindividualdemandsforaparticulargoodorservice.Graphically,individualdemandcurvesaresummedhorizontallytoobtainthemarketdemandcurve.,DeterminantsofDemand,MarketpriceConsumerincomePricesofrelatedgoodsTastesExpectations,ChangeinQuantityDemandedversusChangeinDemand,ChangeinQuantityDemandedMovementalongthedemandcurve.Causedbyachangeinthepriceoftheproduct.,ChangesinQuantityDemanded,0,D1,PriceofCigarettesperPack,NumberofCigarettesSmokedperDay,Ataxthatraisesthepriceofcigarettesresultsinamovementalongthedemandcurve.,A,20,2.00,ChangeinQuantityDemandedversusChangeinDemand,ChangeinDemandAshiftinthedemandcurve,eithertotheleftorright.Causedbyachangeinadeterminantotherthantheprice.,ChangesinDemand,0,D1,PriceofIce-CreamCone,QuantityofIce-CreamCones,D3,D2,Increaseindemand,Decreaseindemand,ConsumerIncome,Asincomeincreasesthedemandforanormalgoodwillincrease.Asincomeincreasesthedemandforaninferiorgoodwilldecrease.,ConsumerIncomeNormalGood,$3.00,2.50,2.00,1.50,1.00,0.50,2,1,3,4,5,6,7,8,9,10,12,11,PriceofIce-CreamCone,QuantityofIce-CreamCones,0,Increaseindemand,Anincreaseinincome.,D1,D2,ConsumerIncomeInferiorGood,$3.00,2.50,2.00,1.50,1.00,0.50,2,1,3,4,5,6,7,8,9,10,12,11,PriceofIce-CreamCone,QuantityofIce-CreamCones,0,Decreaseindemand,Anincreaseinincome.,D1,D2,PricesofRelatedGoodsSubstitutes&Complements,Whenafallinthepriceofonegoodreducesthedemandforanothergood,thetwogoodsarecalledsubstitutes.Whenafallinthepriceofonegoodincreasesthedemandforanothergood,thetwogoodsarecalledcomplements.,ChangeinQuantityDemandedversusChangeinDemand,Supply,Quantitysuppliedistheamountofagoodthatsellersarewillingandabletosell.,LawofSupply,Thelawofsupplystatesthatthereisadirect(positive)relationshipbetweenpriceandquantitysupplied.,DeterminantsofSupply,MarketpriceInputpricesTechnologyExpectationsNumberofproducers,SupplySchedule,Thesupplyscheduleisatablethatshowstherelationshipbetweenthepriceofthegoodandthequantitysupplied.,SupplySchedule,SupplyCurve,Thesupplycurveistheupward-slopinglinerelatingpricetoquantitysupplied.,SupplyCurve,$3.00,2.50,2.00,1.50,1.00,0.50,2,1,3,4,5,6,7,8,9,10,12,11,PriceofIce-CreamCone,QuantityofIce-CreamCones,0,MarketSupply,Marketsupplyreferstothesumofallindividualsuppliesforallsellersofaparticulargoodorservice.Graphically,individualsupplycurvesaresummedhorizontallytoobtainthemarketsupplycurve.,DeterminantsofSupply,MarketpriceInputpricesTechnologyExpectationsNumberofproducers,ChangeinQuantitySuppliedversusChangeinSupply,ChangeinQuantitySuppliedMovementalongthesupplycurve.Causedbyachangeinthemarketpriceoftheproduct.,ChangeinQuantitySupplied,1,5,PriceofIce-CreamCone,QuantityofIce-CreamCones,0,S,1.00,A,C,Ariseinthepriceoficecreamconesresultsinamovementalongthesupplycurve.,ChangeinQuantitySuppliedversusChangeinSupply,ChangeinSupplyAshiftinthesupplycurve,eithertotheleftorright.Causedbyachangeinadeterminantotherthanprice.,ChangeinSupply,PriceofIce-CreamCone,QuantityofIce-CreamCones,0,S1,ChangeinQuantitySuppliedversusChangeinSupply,SupplyandDemandTogether,EquilibriumPriceThepricethatbalancessupplyanddemand.Onagraph,itisthepriceatwhichthesupplyanddemandcurvesintersect.EquilibriumQuantityThequantitythatbalancessupplyanddemand.Onagraphitisthequantityatwhichthesupplyanddemandcurvesintersect.,SupplyandDemandTogether,DemandSchedule,SupplySchedule,At$2.00,thequantitydemandedisequaltothequantitysupplied!,PriceofIce-CreamCone,QuantityofIce-CreamCones,EquilibriumofSupplyandDemand,2,1,3,4,5,6,7,8,9,10,12,11,0,$3.00,2.50,2.00,1.50,1.00,0.50,PriceofIce-CreamCone,QuantityofIce-CreamCones,2,1,3,4,5,6,7,8,9,10,12,11,0,$3.00,2.50,2.00,1.50,1.00,0.50,Supply,Demand,Surplus,ExcessSupply,Surplus,Whenthepriceisabovetheequilibriumprice,thequantitysuppliedexceedsthequantitydemanded.Thereisexcesssupplyorasurplus.Supplierswilllowerthepricetoincreasesales,therebymovingtowardequilibrium.,ExcessDemand,QuantityofIce-CreamCones,PriceofIce-CreamCone,$2.00,0,1,2,3,4,5,6,7,8,9,10,11,12,13,Supply,Demand,$1.50,Shortage,Shortage,Whenthepriceisbelowtheequilibriumprice,thequantitydemandedexceedsthequantitysupplied.Thereisexcessdemandorashortage.Supplierswillraisethepriceduetotoomanybuyerschasingtoofewgoods,therebymovingtowardequilibrium.,ThreeStepsToAnalyzingChangesinEquilibrium,Decidewhethertheeventshiftsthesupplyordemandcurve(orboth).Decidewhetherthecurve(s)shift(s)totheleftortotheright.Examinehowtheshiftaffectsequilibriumpriceandquantity.,HowanIncreaseinDemandAffectstheEquilibrium,PriceofIce-CreamCone,2.00,0,7,QuantityofIce-CreamCones,Supply,Initialequilibrium,D1,1.Hotweatherincreasesthedemandforicecream.,Harcourt,Inc.itemsandderiveditemscopyright2001byHarcourt,Inc.,ShiftsinCurvesversusMovementsalongCurves,Ashiftinthesupplycurveiscalledachangeinsupply.Amovementalongafixedsupplycurveiscalledachangeinquantitysupplied.Ashiftinthedemandcurveiscalledachangeindemand.Amovementalongafixeddemandcurveiscalledachangeinquantitydemanded.,HowaDecreaseinSupplyAffectstheEquilibrium,PriceofIce-CreamCone,2.00,0,1,2,3,4,7,8,9,11,12,QuantityofIce-CreamCones,13,Demand,Initialequilibrium,S1,10,1.Anearthquakereducesthesupplyoficecream.,Newequilibrium,WhatHappenstoPriceandQuantityWhenSupplyorDemandShifts?,Summary,Economistsusethemodelofsupplyanddemandtoanalyzecompetitivemarkets.Thedemandcurveshowshowthequantityofagooddependsupontheprice.,Summary,Accordingtothelawofdemand,asthepriceofagoodrises,thequantitydemandedfalls.Inadditiontoprice,otherdeterminantsofquantitydemandedincludeincome,tastes,expectations,andthepricesofcomplementsandsubstitutes.,Summary,Thesupplycurveshowshowthequantityofagoodsupplieddependsupontheprice.Accordingtothelawofsupply,asthepriceofagoodrises,thequantitysuppliedrises.,Summary,Inadditiontoprice,otherdeterminantsofquantitysuppliedincludeinputprices,technology,a