市场 赞赏经济塑造的 课件

ChapterOneTheMarket---AppreciatingEconomicModelingChapterOne1ThePurposeofthisChapterTobegintounderstandtheartofbuildinganeconomicmodelTobegintounderstandthreebasicelementsofmodelingineconomics:PurposeSimplificationthroughassumptionsValuejudgmentThePurposeofthisChapterTo2ThePurposeofanEconomicModel

Thepurposeofaneconomicmodelistohelpprovidepreciseinsights(精确的洞察力）onaspecificeconomicphenomenon.Thus:Differentphenomenaneedsdifferentmodel;SimplificationbyassumptionisnecessaryThePurposeofanEconomicMod3AnIllustration:ModelingtheApartmentMarketPurpose:Howareapartmentrentsdetermined?Arerents“desirable”?Simplifyingassumptions:apartmentsarecloseordistant,butotherwiseidenticaldistantapartmentsrentsareexogenous(外生变量）andknownmanypotentialrentersandlandlordsAnIllustration:Modelingthe4TwoVeryCommonModelingAssumptionsRationalChoice(理性选择）:Eachpersontriestochoosethebestalternativeavailabletohimorher.Equilibrium（均衡）:economicagentsinteractwitheachother,resultinginanequilibrium,inwhicheachpersonreachesanoptimaldecisiongivenothers’decisions.TwoVeryCommonModelingAssum5ModelingApartmentDemandDemand:Supposethemostanyonepersoniswillingtopaytorentacloseapartmentis$500/month.Then p=$500QD=1.Supposethepricehastodropto$490beforea2ndpersonwouldrent.Then p=$490QD=2.ModelingApartmentDemandDeman6ModelingApartmentDemandTheloweristherentalratep,thelargeristhequantityofcloseapartmentsdemanded

pQD

.Thequantitydemandedvs.pricegraphisthemarketdemandcurveforcloseapartments.ModelingApartmentDemandThel7MarketDemandCurveforApartmentspQDMarketDemandCurveforApartm8ModelingApartmentSupplySupply:Ittakestimetobuildmorecloseapartmentssointhisshort-runthequantityavailableisfixed(atsay100).ModelingApartmentSupplySuppl9MarketSupplyCurveforApartmentspQS100MarketSupplyCurveforApartm10CompetitiveMarketEquilibrium

(竞争性市场均衡）Quantitydemanded=quantityavailable

pricewillneitherrisenorfallsothemarketisatacompetitiveequilibrium.CompetitiveMarketEquilibrium11CompetitiveMarketEquilibriumpQD,QSpe100Peoplewillingtopaypeforcloseapartmentsgetcloseapartments.Peoplenotwillingtopay

peforcloseapartments

getdistantapartments.CompetitiveMarketEquilibrium12ComparativeStatics

（静态比较分析）Whatisexogenousinthemodel?priceofdistantapartmentsquantityofcloseapartmentsincomesofpotentialrenters.Whathappensiftheseexogenousvariableschange?Note：Wearenotanalyzingthetransitionprocessordynamicprocess.ComparativeStatics

（静态比较分析）Wh13ComparativeStaticsSupposethepriceofdistantapartmentrises.Demandforcloseapartmentsincreases(rightwardshift),causingAhigherpriceforcloseapartments.ComparativeStaticsSupposethe14MarketEquilibriumpQD,QSpe100Higherdemandcauseshigher

marketprice;samequantity

traded.MarketEquilibriumpQD,QSpe100H15MoreComparativeStatics

(DoThemYourself)Supposethereweremorecloseapartments.Or,renters’incomerises;MoreComparativeStatics

(Do16ElaborationoftheBasicModel:TaxationPolicyAnalysisLocalgovernmenttaxesapartmentowners.Whathappenstopricequantityofcloseapartmentsrented?Isanyofthetax“passed”torenters?ElaborationoftheBasicMo17TaxationPolicyAnalysisMarketsupplyisunaffected.Marketdemandisunaffected.Sothecompetitivemarketequilibriumisunaffectedbythetax.Priceandthequantityofcloseapartmentsrentedarenotchanged.Landlordspayallofthetax.TaxationPolicyAnalysisMarket18ImperfectlyCompetitiveMarket

Case1：AMonopolisticLandlordLandlordsetsarentalpricepherentsD(p)apartments.Revenue=pD(p).HechoosesptomaximizespD(p),subjecttoD(p)<=S(totalnumberofapartmentsinhishands)Typically,hisoptimalpissuchthat D(p)<S,thatis,therearevacantapartments.ImperfectlyCompetitiveMarke19MonopolisticMarketEquilibriumpQD,QSMiddle

priceMiddleprice,mediumquantity

demanded,largerrevenue.

Monopolistdoesnotrentallthe

closeapartments.100Vacantcloseapartments.MonopolisticMarketEquilibriu20ImperfectlyCompetitiveMarketCase2：PerfectlyDiscriminatoryMonopolisticLandlordImaginethemonopolistknewwillingness-to-payofeverybody,Charge$500tothemostwilling-to-pay,charge$490tothe2ndmostwilling-to-pay,etc.ImperfectlyCompetitiveMarke21DiscriminatoryMonopolisticMarketEquilibriumpQD,QS100p1=$5001DiscriminatoryMonopolisticMa22DiscriminatoryMonopolisticMarketEquilibriumpQD,QS100p1=$500p2=$49012DiscriminatoryMonopolisticMa23DiscriminatoryMonopolisticMarketEquilibriumpQD,QS100p1=$500p2=$49012p3=$4753DiscriminatoryMonopolisticMa24DiscriminatoryMonopolisticMarketEquilibriumpQD,QS100p1=$500p2=$49012p3=$4753DiscriminatoryMonopolisticMa25DiscriminatoryMonopolisticMarketEquilibriumpQD,QS100p1=$500p2=$49012p3=$4753peDiscriminatorymonopolist

chargesthecompetitivemarket

pricetothelastrenter,and

rentsthecompetitivequantity

ofcloseapartments.DiscriminatoryMonopolisticMa26RentControl

(房租管制）Localgovernmentimposesamaximumlegalprice,pmax<pe,thecompetitiveprice.RentControl

(房租管制）Localgover27MarketEquilibriumpQD,QSpe100pmaxExcessdemandThe100closeapartmentsarenolongerallocatedby

willingness-to-pay(lottery,lines,

largefamiliesfirst?).MarketEquilibriumpQD,QSpe100p28ValueJudgement

（价值判断）Whichofthefollowingisbetter?RentcontrolPerfectcompetitionMonopolyDiscriminatorymonopolyBut,whatdoyoumeanby“better”?ValueJudgement

（价值判断）Whicho29ParetoEfficiency

（帕累托效率）VilfredoPareto;1848-1923.AParetooutcomeallowsno“wastedwelfare”;i.e.theonlywayoneperson’swelfarecanbeimprovedistoloweranotherperson’swelfare.ParetoEfficiency

（帕累托效率）Vilfr30ParetoEfficiencyAParetoinefficientoutcomemeansthereremainunrealizedmutualgains-to-trade.Anymarketoutcomethatachievesallpossiblegains-to-trademustbeParetoefficient.ParetoEfficiencyAParetoinef31ParetoEfficiencyCompetitiveequilibrium:allcloseapartmentrentersvaluethematthemarketpricepeormoreallothersvaluecloseapartmentsatlessthanpesonomutuallybeneficialtradesremainsotheoutcomeisParetoefficient.ParetoEfficiencyCompetitivee32ParetoEfficiencyDiscriminatoryMonopoly:assignmentofapartmentsisthesameaswiththeperfectlycompetitivemarketsothediscriminatorymonopolyoutcomeisalsoParetoefficient.ParetoEfficiencyDiscriminator33ParetoEfficiencyMonopoly:notallapartmentsareoccupiedsoadistantapartmentrentercouldbeassignedacloseapartmentandhavehigherwelfarewithoutloweringanybodyelse’swelfare.sothemonopolyoutcomeisParetoinefficient.ParetoEfficiencyMonopoly:34ParetoEfficiencyRentControl:somecloseapartmentsareassignedtorentersvaluingthematbelowthecompetitivepricepesomerentersvaluingacloseapartmentabovepedon’tgetcloseapartmentsParetoinefficientoutcome.ParetoEfficiencyRentControl:35FurtherExtensionsoftheModelOvertime,willthesupplyofcloseapartmentsincrease?rentcontroldecreasethesupplyofapartments?amonopolistsupplymoreapartmentsthanacompetitiverentalmarket?FurtherExtensionsoftheMod36AQuickSummaryEconomicmodelingservesaspecificpurpose;Forthepurpose,aneconomicmodelneedstomakesimplifyingassumptions;Economistsdohavevaluejudgments,whicharebasedonspecifiedcriterion.AQuickSummaryEconomicmodeli37ChapterOneTheMarket---AppreciatingEconomicModelingChapterOne38ThePurposeofthisChapterTobegintounderstandtheartofbuildinganeconomicmodelTobegintounderstandthreebasicelementsofmodelingineconomics:PurposeSimplificationthroughassumptionsValuejudgmentThePurposeofthisChapterTo39ThePurposeofanEconomicModel

Thepurposeofaneconomicmodelistohelpprovidepreciseinsights(精确的洞察力）onaspecificeconomicphenomenon.Thus:Differentphenomenaneedsdifferentmodel;SimplificationbyassumptionisnecessaryThePurposeofanEconomicMod40AnIllustration:ModelingtheApartmentMarketPurpose:Howareapartmentrentsdetermined?Arerents“desirable”?Simplifyingassumptions:apartmentsarecloseordistant,butotherwiseidenticaldistantapartmentsrentsareexogenous(外生变量）andknownmanypotentialrentersandlandlordsAnIllustration:Modelingthe41TwoVeryCommonModelingAssumptionsRationalChoice(理性选择）:Eachpersontriestochoosethebestalternativeavailabletohimorher.Equilibrium（均衡）:economicagentsinteractwitheachother,resultinginanequilibrium,inwhicheachpersonreachesanoptimaldecisiongivenothers’decisions.TwoVeryCommonModelingAssum42ModelingApartmentDemandDemand:Supposethemostanyonepersoniswillingtopaytorentacloseapartmentis$500/month.Then p=$500QD=1.Supposethepricehastodropto$490beforea2ndpersonwouldrent.Then p=$490QD=2.ModelingApartmentDemandDeman43ModelingApartmentDemandTheloweristherentalratep,thelargeristhequantityofcloseapartmentsdemanded

pQD

.Thequantitydemandedvs.pricegraphisthemarketdemandcurveforcloseapartments.ModelingApartmentDemandThel44MarketDemandCurveforApartmentspQDMarketDemandCurveforApartm45ModelingApartmentSupplySupply:Ittakestimetobuildmorecloseapartmentssointhisshort-runthequantityavailableisfixed(atsay100).ModelingApartmentSupplySuppl46MarketSupplyCurveforApartmentspQS100MarketSupplyCurveforApartm47CompetitiveMarketEquilibrium

(竞争性市场均衡）Quantitydemanded=quantityavailable

pricewillneitherrisenorfallsothemarketisatacompetitiveequilibrium.CompetitiveMarketEquilibrium48CompetitiveMarketEquilibriumpQD,QSpe100Peoplewillingtopaypeforcloseapartmentsgetcloseapartments.Peoplenotwillingtopay

peforcloseapartments

getdistantapartments.CompetitiveMarketEquilibrium49ComparativeStatics

（静态比较分析）Whatisexogenousinthemodel?priceofdistantapartmentsquantityofcloseapartmentsincomesofpotentialrenters.Whathappensiftheseexogenousvariableschange?Note：Wearenotanalyzingthetransitionprocessordynamicprocess.ComparativeStatics

（静态比较分析）Wh50ComparativeStaticsSupposethepriceofdistantapartmentrises.Demandforcloseapartmentsincreases(rightwardshift),causingAhigherpriceforcloseapartments.ComparativeStaticsSupposethe51MarketEquilibriumpQD,QSpe100Higherdemandcauseshigher

marketprice;samequantity

traded.MarketEquilibriumpQD,QSpe100H52MoreComparativeStatics

(DoThemYourself)Supposethereweremorecloseapartments.Or,renters’incomerises;MoreComparativeStatics

(Do53ElaborationoftheBasicModel:TaxationPolicyAnalysisLocalgovernmenttaxesapartmentowners.Whathappenstopricequantityofcloseapartmentsrented?Isanyofthetax“passed”torenters?ElaborationoftheBasicMo54TaxationPolicyAnalysisMarketsupplyisunaffected.Marketdemandisunaffected.Sothecompetitivemarketequilibriumisunaffectedbythetax.Priceandthequantityofcloseapartmentsrentedarenotchanged.Landlordspayallofthetax.TaxationPolicyAnalysisMarket55ImperfectlyCompetitiveMarket

Case1：AMonopolisticLandlordLandlordsetsarentalpricepherentsD(p)apartments.Revenue=pD(p).HechoosesptomaximizespD(p),subjecttoD(p)<=S(totalnumberofapartmentsinhishands)Typically,hisoptimalpissuchthat D(p)<S,thatis,therearevacantapartments.ImperfectlyCompetitiveMarke56MonopolisticMarketEquilibriumpQD,QSMiddle

priceMiddleprice,mediumquantity

demanded,largerrevenue.

Monopolistdoesnotrentallthe

closeapartments.100Vacantcloseapartments.MonopolisticMarketEquilibriu57ImperfectlyCompetitiveMarketCase2：PerfectlyDiscriminatoryMonopolisticLandlordImaginethemonopolistknewwillingness-to-payofeverybody,Charge$500tothemostwilling-to-pay,charge$490tothe2ndmostwilling-to-pay,etc.ImperfectlyCompetitiveMarke58DiscriminatoryMonopolisticMarketEquilibriumpQD,QS100p1=$5001DiscriminatoryMonopolisticMa59DiscriminatoryMonopolisticMarketEquilibriumpQD,QS100p1=$500p2=$49012DiscriminatoryMonopolisticMa60DiscriminatoryMonopolisticMarketEquilibriumpQD,QS100p1=$500p2=$49012p3=$4753DiscriminatoryMonopolisticMa61DiscriminatoryMonopolisticMarketEquilibriumpQD,QS100p1=$500p2=$49012p3=$4753DiscriminatoryMonopolisticMa62DiscriminatoryMonopolisticMarketEquilibriumpQD,QS100p1=$500p2=$49012p3=$4753peDiscriminatorymonopolist

chargesthecompetitivemarket

pricetothelastrenter,and

rentsthecompetitivequantity

ofcloseapartments.DiscriminatoryMonopolisticMa63RentControl

(房租管制）Localgovernmentimposesamaximumlegalprice,pmax<pe,thecompetitiveprice.RentControl

(房租管制）Localgover64MarketEquilibriumpQD,QSpe100pmaxExcessdemandThe100closeapartmentsarenolongerallocatedby

willingness-to-pay(lottery,lines,

largefamiliesfirst?).MarketEquilibriumpQD,QSpe100p65ValueJudgement

（价值判断）Whichofthefollowingisbetter?RentcontrolPerfectcompetitionMonopolyDiscriminatorymonopolyBut,whatdoyoumeanby“better”?ValueJudgement

（价值判断）Whicho66ParetoEfficiency

（帕累托效率）VilfredoPareto;1848-1923.AParetooutcomeallowsno“wastedwelfare”;i.e.theonlywayoneperson’swelfarecanbeimprovedistoloweranotherperson’swelfare.ParetoEfficiency

（帕累托效率）Vilfr67ParetoEfficiencyAParetoinefficientoutcomemeansthereremainunrealizedmutualgains-to-trade.Anymarketoutcomethatachieves