清华微通道精确洞察力

ThefollowingcontentisbasedontheslidesprovidedbyNortonPublishersforHalVarian:IntermediateMicroeconomics4theditionandmodifiedbyProfessorDavidDaokuiLiforthepurposeofteachingIntermediateMicroeconomicsatTsinghuaUniversity.OtherusesofthecontentwithouttheapprovalofNortonPublishers,TsinghuaUniversity,andProfessorDavidDaokuiLiarestrictlyprohibited.AllrightsprovidedbyrelevantlawsareThePurposeofthisTobegintounderstandtheartofbuildinganeconomicmodelTobegintounderstandthreebasicelementsofmodelingineconomics:ThePurposeofanEconomic Thepurposeofaneconomicmodelistohelpprovidepreciseinsights精确的洞察力）onaspecificeconomicSimplificationbyassumptionisAnIllustration:ModelingPurpose:Howareapartmentrentsapartmentsarecloseordistant,butotherwisedistantapartmentsrentsareexogenous(外生变量）andknownRationalChoice(理性选择）:Eachpersontriestochoosethebestalternativeavailabletohimorher.Equilibrium（均衡）economicagentsinteractwitheachother,resultinginanequilibrium,inwhicheachpersonreachesanoptimaldecisiongivenothers’decisions.Demand:Supposethemostanyonepersoniswillingtopaytorentacloseapartmentis$500/month.Then p=$500QD=Supposethepricehastodropto$490beforea2ndpersonwouldrent.Then =$490QD=Theloweristherentalratep,thelargeristhequantityofcloseapartmentsdemandedpflQDThequantitydemandedvs.pricegraphisthemarketdemandcurveforcloseapartments.MarketDemandCurvepSupply:Ittakestimetobuildmorecloseapartmentssointhisshort-runthequantityavailableisfixed(atsay100).MarketSupplyCurvep Quantitydemanded=quantitypricewillneitherrisenorsothemarketisatacompetitivepPeoplewillingtopaypeforcloseapartmentsgetclosePeoplenotwillingtopaypeforcloseapartmentsgetdistant WhatisexogenousinthepriceofdistantquantityofcloseincomesofpotentialWhathappensiftheseexogenousvariablesNote：Wearenotanalyzingthetransitionprocessordynamicprocess.SupposethepriceofdistantapartmentDemandforcloseapartmentsincreases(rightwardshift),causingAhigherpriceforclosepHigherdemandcausesmarketprice;samequantity (DoThemSupposethereweremoreclose oftheBasicWhathappensquantityofcloseapartmentsIsanyofthetax“passed”toMarketsupplyisMarketdemandisSothecompetitivemarketequilibriumisunaffectedbythetax.Priceandthequantityofcloseapartmentsrentedarenotchanged.LandlordspayalloftheImperfectlyCompetitiveCase1：AMonopolisticLandlordsetsarentalpricepherentsD(p)Revenue=HechoosesptomaximizespD(p),subjectto<=S(totalnumberofapartmentsinhisTypically,hisoptimalpissuchD(p)<S,thatis,therearevacant Middleprice,mediumquantitydemanded,largerrevenue.Monopolistdoesnotrentallthecloseapartments.

Vacantclose ImperfectlyCompetitiveCase2：PerfectlyDiscriminatoryMonopolisticLandlordImaginethemonopolistkneweveryone’sCharge$500tothemostwilling-to-charge$490tothe2ndmostwilling-to-pay,p pp2 pp2=$490p3123 p2=$490p3123 p2=$490p3

Discriminatorymonopolistchargesthecompetitivemarketpricetothelastrenter,andrentsthecompetitivequantityofcloseapartments.123 Localgovernmentimposesamaximumlegalprice,pmax<pe,thecompetitiveprice. The100closeapartmentsarenolongerallocatedbylargefamiliesfirst?).

ExcessValueWhichofthefollowingisBut,whatdoyoumeanbyAParetooutcomeallowsno“wastedi.e.theonlywayoneperson’swelfarecanbeimprovedistoloweranotherperson’swelfare.AParetoinefficientoutcomemeansthereremainunrealizedmutualgains-to-trade.Anymarketoutcomethatachievesallpossiblegains-to-trademustbeParetoefficient.allcloseapartmentrentersvaluethematthemarketpricepeormoreallothersvaluecloseapartmentsatlessthansonomutuallybeneficialtradessotheoutcomeisParetoassignmentofapartmentsisthesameaswiththeperfectlycompetitivemarketsothediscriminatorymonopolyoutcomeisalsoParetoefficient.notallapartmentsaresoadistantapartmentrentercouldbeassignedacloseapartmentandhavehigherwelfarewithoutloweringanybodyelse’swelfare.sothemonopolyoutcomeisParetosomecloseapartmentsareassignedtorentersvaluingthematbelowthecompetitivepricepesomerentersvaluingacloseapartmentabovepedon’tgetcloseapartmentsAQuickEconomicmodelingservesaspecificForthepurpose,aneconomicmodelneedstomakesimplifyingassumptions;Economistsdohavevalue