微观经济学原理曼昆英文第四章PPT课件

TheMarketForcesofSupplyandDemand Economics PRINCIPLESOF N GregoryMankiw 4 Inthischapter lookfortheanswerstothesequestions Whatfactorsaffectbuyers demandforgoods Whatfactorsaffectsellers supplyofgoods Howdosupplyanddemanddeterminethepriceofagoodandthequantitysold Howdochangesinthefactorsthataffectdemandorsupplyaffectthemarketpriceandquantityofagood Howdomarketsallocateresources 1 2 MarketsandCompetition Amarketisagroupofbuyersandsellersofaparticularproduct Acompetitivemarketisonewithmanybuyersandsellers eachhasanegligibleeffectonprice Inaperfectlycompetitivemarket AllgoodsexactlythesameBuyers sellerssonumerousthatnoonecanaffectmarketprice eachisa pricetaker Inthischapter weassumemarketsareperfectlycompetitive 0 3 Demand Thequantitydemandedofanygoodistheamountofthegoodthatbuyersarewillingandabletopurchase Lawofdemand theclaimthatthequantitydemandedofagoodfallswhenthepriceofthegoodrises otherthingsequal 0 4 TheDemandSchedule Demandschedule atablethatshowstherelationshipbetweenthepriceofagoodandthequantitydemandedExample Helen sdemandforlattes NoticethatHelen spreferencesobeytheLawofDemand 0 5 Helen sDemandSchedule Curve 0 MarketDemandversusIndividualDemand Thequantitydemandedinthemarketisthesumofthequantitiesdemandedbyallbuyersateachprice SupposeHelenandKenaretheonlytwobuyersintheLattemarket Qd quantitydemanded MarketQd 0 6 7 P Q TheMarketDemandCurveforLattes 0 8 DemandCurveShifters Thedemandcurveshowshowpriceaffectsquantitydemanded otherthingsbeingequal These otherthings arenon pricedeterminantsofdemand i e thingsthatdeterminebuyers demandforagood otherthanthegood sprice ChangesinthemshifttheDcurve 0 9 DemandCurveShifters ofBuyers Increasein ofbuyersincreasesquantitydemandedateachprice shiftsDcurvetotheright 0 10 Supposethenumberofbuyersincreases Then ateachP Qdwillincrease by5inthisexample 0 DemandCurveShifters ofBuyers 11 Demandforanormalgoodispositivelyrelatedtoincome Increaseinincomecausesincreaseinquantitydemandedateachprice shiftsDcurvetotheright Demandforaninferiorgoodisnegativelyrelatedtoincome AnincreaseinincomeshiftsDcurvesforinferiorgoodstotheleft DemandCurveShifters Income 0 12 Twogoodsaresubstitutesifanincreaseinthepriceofonecausesanincreaseindemandfortheother Example pizzaandhamburgers Anincreaseinthepriceofpizzaincreasesdemandforhamburgers shiftinghamburgerdemandcurvetotheright Otherexamples CokeandPepsi laptopsanddesktopcomputers CDsandmusicdownloads DemandCurveShifters PricesofRelatedGoods 0 13 Twogoodsarecomplementsifanincreaseinthepriceofonecausesafallindemandfortheother Example computersandsoftware Ifpriceofcomputersrises peoplebuyfewercomputers andthereforelesssoftware Softwaredemandcurveshiftsleft Otherexamples collegetuitionandtextbooks bagelsandcreamcheese eggsandbacon DemandCurveShifters PricesofRelatedGoods 0 14 AnythingthatcausesashiftintastestowardagoodwillincreasedemandforthatgoodandshiftitsDcurvetotheright Example TheAtkinsdietbecamepopularinthe 90s causedanincreaseindemandforeggs shiftedtheeggdemandcurvetotheright DemandCurveShifters Tastes 0 15 Expectationsaffectconsumers buyingdecisions Examples Ifpeopleexpecttheirincomestorise theirdemandformealsatexpensiverestaurantsmayincreasenow Iftheeconomysoursandpeopleworryabouttheirfuturejobsecurity demandfornewautosmayfallnow DemandCurveShifters Expectations 0 16 Summary VariablesThatInfluenceBuyers VariableAchangeinthisvariable Price causesamovementalongtheDcurve ofbuyers shiftstheDcurveIncome shiftstheDcurvePriceofrelatedgoods shiftstheDcurveTastes shiftstheDcurveExpectations shiftstheDcurve 0 A ThepriceofiPodsfallsB ThepriceofmusicdownloadsfallsC ThepriceofCDsfalls ACTIVELEARNING1DemandCurve 17 Drawademandcurveformusicdownloads Whathappenstoitineachofthefollowingscenarios Why 18 Supply Thequantitysuppliedofanygoodistheamountthatsellersarewillingandabletosell Lawofsupply theclaimthatthequantitysuppliedofagoodriseswhenthepriceofthegoodrises otherthingsequal 0 19 TheSupplySchedule Supplyschedule Atablethatshowstherelationshipbetweenthepriceofagoodandthequantitysupplied Example Starbucks supplyoflattes NoticethatStarbucks supplyscheduleobeystheLawofSupply 0 20 Starbucks SupplySchedule Curve P Q 0 MarketSupplyversusIndividualSupply Thequantitysuppliedinthemarketisthesumofthequantitiessuppliedbyallsellersateachprice SupposeStarbucksandJittersaretheonlytwosellersinthismarket Qs quantitysupplied MarketQs 0 21 22 TheMarketSupplyCurve 0 23 SupplyCurveShifters Thesupplycurveshowshowpriceaffectsquantitysupplied otherthingsbeingequal These otherthings arenon pricedeterminantsofsupply ChangesinthemshifttheScurve 0 24 SupplyCurveShifters InputPrices Examplesofinputprices wages pricesofrawmaterials Afallininputpricesmakesproductionmoreprofitableateachoutputprice sofirmssupplyalargerquantityateachprice andtheScurveshiftstotheright 0 25 Supposethepriceofmilkfalls Ateachprice thequantityofLattessuppliedwillincrease by5inthisexample SupplyCurveShifters InputPrices 0 26 SupplyCurveShifters Technology Technologydetermineshowmuchinputsarerequiredtoproduceaunitofoutput Acost savingtechnologicalimprovementhasthesameeffectasafallininputprices shiftsScurvetotheright 0 27 SupplyCurveShifters ofSellers Anincreaseinthenumberofsellersincreasesthequantitysuppliedateachprice shiftsScurvetotheright 0 28 SupplyCurveShifters Expectations Example EventsintheMiddleEastleadtoexpectationsofhigheroilprices Inresponse ownersofTexasoilfieldsreducesupplynow savesomeinventorytoselllateratthehigherprice Scurveshiftsleft Ingeneral sellersmayadjustsupply whentheirexpectationsoffuturepriceschange Ifgoodnotperishable 0 29 Summary VariablesthatInfluenceSellers VariableAchangeinthisvariable Price causesamovementalongtheScurveInputPrices shiftstheScurveTechnology shiftstheScurve ofSellers shiftstheScurveExpectations shiftstheScurve 0 ACTIVELEARNING2SupplyCurve 30 Drawasupplycurvefortaxreturnpreparationsoftware Whathappenstoitineachofthefollowingscenarios A Retailerscutthepriceofthesoftware B Atechnologicaladvanceallowsthesoftwaretobeproducedatlowercost C Professionaltaxreturnpreparersraisethepriceoftheservicestheyprovide 31 SupplyandDemandTogether Equilibrium Phasreachedthelevelwherequantitysuppliedequalsquantitydemanded 0 32 Equilibriumprice thepricethatequatesquantitysuppliedwithquantitydemanded 0 33 Equilibriumquantity thequantitysuppliedandquantitydemandedattheequilibriumprice 0 34 Surplus a k a excesssupply whenquantitysuppliedisgreaterthanquantitydemanded Surplus Example IfP 5 thenQD 9lattes andQS 25lattes resultinginasurplusof16lattes 0 35 Surplus a k a excesssupply whenquantitysuppliedisgreaterthanquantitydemanded Facingasurplus sellerstrytoincreasesalesbycuttingprice ThiscausesQDtorise whichreducesthesurplus andQStofall 0 36 Surplus a k a excesssupply whenquantitysuppliedisgreaterthanquantitydemanded Facingasurplus sellerstrytoincreasesalesbycuttingprice ThiscausesQDtoriseandQStofall Surplus Pricescontinuetofalluntilmarketreachesequilibrium 0 37 Shortage a k a excessdemand whenquantitydemandedisgreaterthanquantitysupplied Example IfP 1 thenQD 21lattes andQS 5lattes resultinginashortageof16lattes Shortage 0 38 Shortage a k a excessdemand whenquantitydemandedisgreaterthanquantitysupplied Facingashortage sellersraisetheprice causingQDtofall whichreducestheshortage andQStorise 0 39 Shortage a k a excessdemand whenquantitydemandedisgreaterthanquantitysupplied Facingashortage sellersraisetheprice causingQDtofall andQStorise Shortage Pricescontinuetoriseuntilmarketreachesequilibrium 0 40 ThreeStepstoAnalyzingChangesinEq m Todeterminetheeffectsofanyevent 1 DecidewhethereventshiftsScurve Dcurve orboth 2 Decideinwhichdirectioncurveshifts 3 Usesupply demanddiagramtoseehowtheshiftchangeseq mPandQ 41 EXAMPLE TheMarketforHybridCars 42 STEP1 Dcurveshiftsbecausepriceofgasaffectsdemandforhybrids Scurvedoesnotshift becausepriceofgasdoesnotaffectcostofproducinghybrids STEP2 Dshiftsrightbecausehighgaspricemakeshybridsmoreattractiverelativetoothercars EXAMPLE1 AShiftinDemand EVENTTOBEANALYZED Increaseinpriceofgas STEP3 Theshiftcausesanincreaseinpriceandquantityofhybridcars 43 EXAMPLE1 AShiftinDemand P2 Q2 Notice WhenPrises producerssupplyalargerquantityofhybrids eventhoughtheScurvehasnotshifted Alwaysbecarefultodistinguishb washiftinacurveandamovementalongthecurve TermsforShiftvs MovementAlongCurve Changeinsupply ashiftintheScurveoccurswhenanon pricedeterminantofsupplychanges liketechnologyorcosts Changeinthequantitysupplied amovementalongafixedScurveoccurswhenPchangesChangeindemand ashiftintheDcurveoccurswhenanon pricedeterminantofdemandchanges likeincomeor ofbuyers Changeinthequantitydemanded amovementalongafixedDcurveoccurswhenPchanges 44 45 STEP1 Scurveshiftsbecauseeventaffectscostofproduction Dcurvedoesnotshift becauseproductiontechnologyisnotoneofthefactorsthataffectdemand STEP2 Sshiftsrightbecauseeventreducescost makesproductionmoreprofitableatanygivenprice EXAMPLE2 AShiftinSupply EVENT Newtechnologyreducescostofproducinghybridcars STEP3 Theshiftcausespricetofallandquantitytorise 46 EXAMPLE3 AShiftinBothSupplyandDemand EVENTS priceofgasrisesANDnewtechnologyreducesproductioncosts STEP1 Bothcurvesshift STEP2 Bothshifttotheright STEP3 Qrises buteffectonPisambiguous Ifdemandincreasesmorethansupply Prises 47 EXAMPLE3 AShiftinBothSupplyandDemand STEP3 cont EVENTS priceofgasrisesANDnewtechnologyreducesproductioncosts Butifsupplyincreasesmorethandemand Pfalls ACTIVELEARNING3Shiftsinsupplyanddemand 48 Usethethree stepmethodtoanalyzetheeffectsofeacheventontheequilibriumpriceandquantityofmusicdownloads EventA AfallinthepriceofCDsEventB Sellersofmusicdownloadsnegotiateareductionintheroyaltiestheymustpayforeachsongtheysell EventC EventsAandBbothoccur 49 CONCLUSION HowPricesAllocateResources OneoftheTenPrinciplesfromChapter1 Marketsareusuallyagoodwaytoorganizeeconomicactivity Inmarketeconomies pricesadjusttobalancesupplyanddemand Theseequilibriumpricesarethesignalsthatguideeconomicdecisionsandtherebyallocatescarceresources CHAPTERSUMMARY Acompetitivemarkethasmanybuyersandsellers eachofwhomhaslittleornoinfluenceonthemarketprice Economistsusethesupplyanddemandmodeltoanalyzecompetitivemarkets Thedownward slopingdemandcurvereflectstheLawofDemand whichstatesthatthequant