中级微观课件

中级微观经济学

2015叶建亮浙江大学经济学院课程说明教材：H.Varian：《IntermediateMicroeconomics:AmodernApproach》(6th)；《微观经济学：现代观点》（中译本），上海三联书店，2006年。课程说明参考书：平狄克、鲁宾费尔德：《微观经济学》(第四版)，中国人民大学出版社，2000年蒋中一：《数理经济学的基本方法》，商务印书馆，1999年。课程说明讨论与疑问：可通过以下方式联系：周五上午9：00—9：40，紫金港西一313教师休息室.

考试：80％来源于平时上课和课后作业；20％理解与应用。TheTheoryofEconomicsdoesnot

furnishabodyofsettledconclusions

immediatelyapplicabletopolicy.Itis

amethodratherthanadoctrine,an

apparatusofthemind,atechniqueof

thinkingwhichhelpsitspossessorto

drawcorrectconclusions

---JohnMaynardKeynesIsEconomicsUseful?ingathinkerChangesthewayyouviewlifeandunderstandproblemsAnallroundmajorCourseOutlineConsumertheory(1-15)Producertheory(18-27)Marketequilibrium(16-17,30-32)SpecialtopicsonequilibriumEconomicModelingWhatcauseswhatineconomicsystems?Whichvariablesaredeterminedoutsidethemodel(exogenous)Whichvariablesaretobedeterminedbythemodel(endogenous)Atwhatlevelofdetailshallwemodelaneconomicphenomenon?ModelingtheApartmentMarketCentralquestion:Howareapartmentrentsdetermined?Suppose(simplifyingassumptions)apartmentsarecloseordistant,butotherwiseidenticaldistantapartmentsrentsareexogenousandknownmanypotentialrentersandlandlords,i.e.,competitivemarketANormativeQuestionWilltheallocationofapartmentsbedesirable?Needtoknow:Whowillrentcloseapartments?Atwhatprice?TwoPrinciplesinEconomicsOptimization:Eachpersontriestochoosethebestalternativeavailabletohimorher.Equilibrium:Marketpriceadjustsuntilquantitydemandedequalsquantitysupplied.ModelingIndividualDemandDiscretecommodity:0or1unitChooseeitherdistantorcloseapartmentCloseapartmentsaremoredesirablebutmoreexpensiveTendtochoosecloseapartmentifDistantapartmentsarealsoexpensive.Highere.Decide:Themaximumrentyouarewillingtopayforacloseapartment.ModelingMarketDemandDemand:Supposethemostanyonepersoniswillingtopaytorentacloseapartmentis$500/month.Then p=$500

QD=1.Supposethepricehastodropto$490beforea2ndpersonwouldrent.Then p=$490

QD=2.ModelingApartmentDemandTheloweristherentalratep,thelargeristhequantityofcloseapartmentsdemanded

p

QD

.Thequantitydemandedvs.pricegraphisthemarketdemandcurveforcloseapartments.MarketDemandCurveforApartmentspQDModelingApartmentSupplySupply:Ittakestimetobuildmorecloseapartmentssointhisshort-runthequantityavailableisfixed(atsay100).MarketSupplyCurveforApartmentspQS100CompetitiveMarketEquilibrium“low”rentalprice

quantitydemandedofcloseapartmentsexceedsquantityavailable

pricewillrise.“high”rentalprice

quantitydemandedlessthanquantityavailable

pricewillfall.CompetitiveMarketEquilibriumQuantitydemanded=quantityavailable

pricewillneitherrisenorfallsothemarketisatacompetitiveequilibrium.CompetitiveMarketEquilibriumpQD,QS100CompetitiveMarketEquilibriumpQD,QSpe100CompetitiveMarketEquilibriumpQD,QSpe100Peoplewillingtopaypeforcloseapartmentsgetcloseapartments.CompetitiveMarketEquilibriumpQD,QSpe100Peoplewillingtopaypeforcloseapartmentsgetcloseapartments.Peoplenotwillingtopay

peforcloseapartments

getdistantapartments.CompetitiveMarketEquilibriumQ:Whorentsthecloseapartments?A:Thosemostwillingtopay.Q:Whorentsthedistantapartments?A:Thoseleastwillingtopay.Sothecompetitivemarketallocationisby“willingness-to-pay”.ComparativeStaticsWhatisexogenousinthemodel?priceofdistantapartmentsquantityofcloseapartmentsesofpotentialrenters.Whathappensiftheseexogenousvariableschange?ComparativeStaticsSupposethepriceofdistantapartmentrises.Demandforcloseapartmentsincreases(rightwardshift),causingahigherpriceforcloseapartments.MarketEquilibriumpQD,QSpe100MarketEquilibriumpQD,QSpe100HigherdemandMarketEquilibriumpQD,QSpe100Higherdemandcauseshigher

marketprice;samequantity

traded.ComparativeStaticsSupposethereweremorecloseapartments.Supplyisgreater,sothepriceforcloseapartmentsfalls.MarketEquilibriumpQD,QSpe100MarketEquilibriumpQD,QS100HighersupplypeMarketEquilibriumpQD,QSpe100Highersupplycausesa

lowermarketpriceanda

largerquantitytraded.ComparativeStaticsSupposepotentialrenters’esrise,increasingtheirwillingness-to-payforcloseapartments.Demandrises(upwardshift),causinghigherpriceforcloseapartments.MarketEquilibriumpQD,QSpe100MarketEquilibriumpQD,QSpe100Higherescause

higherwillingness-to-payMarketEquilibriumpQD,QSpe100Higherescause

higherwillingness-to-pay,

highermarketprice,and

thesamequantitytraded.

ImperfectlyCompetitiveMarketsAmongstmanypossibilitiesare:amonopolisticlandlordaperfectlydiscriminatorymonopolisticlandlordacompetitivemarketsubjecttorentcontrol.AMonopolisticLandlordWhenthelandlordsetsarentalpricepherentsD(p)apartments.Revenue=pD(p).Revenueislowifp

0RevenueislowifpissohighthatD(p)0.Anintermediatevalueforpmaximizesrevenue.MonopolisticMarketEquilibriumpQDLow

priceLowprice,highquantity

demanded,lowrevenue.MonopolisticMarketEquilibriumpQDHigh

priceHighprice,lowquantity

demanded,lowrevenue.MonopolisticMarketEquilibriumpQDMiddle

priceMiddleprice,mediumquantity

demanded,largerrevenue.MonopolisticMarketEquilibriumpQD,QSMiddle

priceMiddleprice,mediumquantity

demanded,largerrevenue.

Monopolistdoesnotrentallthe

closeapartments.100MonopolisticMarketEquilibriumpQD,QSMiddle

priceMiddleprice,mediumquantity

demanded,largerrevenue.

Monopolistdoesnotrentallthe

closeapartments.100Vacantcloseapartments.PerfectlyDiscriminatoryMonopolisticLandlordImaginethemonopolistkneweveryone’swillingness-to-pay.Charge$500tothemostwilling-to-pay,charge$490tothe2ndmostwilling-to-pay,etc.DiscriminatoryMonopolisticMarketEquilibriumpQD,QS100p1=$5001DiscriminatoryMonopolisticMarketEquilibriumpQD,QS100p1=$500p2=$49012DiscriminatoryMonopolisticMarketEquilibriumpQD,QS100p1=$500p2=$49012p3=$4753DiscriminatoryMonopolisticMarketEquilibriumpQD,QS100p1=$500p2=$49012p3=$4753DiscriminatoryMonopolisticMarketEquilibriumpQD,QS100p1=$500p2=$49012p3=$4753peDiscriminatorymonopolist

chargesthecompetitivemarket

pricetothelastrenter,and

rentsthecompetitivequantity

ofcloseapartments.RentControlLocalgovernmentimposesamaximumlegalprice,pmax<pe,thecompetitiveprice.MarketEquilibriumpQD,QSpe100MarketEquilibriumpQD,QSpe100pmaxMarketEquilibriumpQD,QSpe100pmaxExcessdemandMarketEquilibriumpQD,QSpe100pmaxExcessdemandThe100closeapartmentsarenolongerallocatedby

willingness-to-pay(lottery,lines,

largefamiliesfirst?).WhichMarketesAreDesirable?Whichisbetter?RentcontrolPerfectcompetitionMonopolyDiscriminatorymonopolyParetoEfficiencyVilfredoPareto;1848-1923.AParetoeallowsno“wastedwelfare”;i.e.theonlywayoneperson’swelfarecanbeimprovedistoloweranotherperson’swelfare.ParetoEfficiencyJillhasanapartment;Jackdoesnot.Jillvaluestheapartmentat$200;Jackwouldpay$400forit.JillcouldsublettheapartmenttoJackfor$300.Bothgain,soitwasParetoinefficientforJilltohavetheapartment.CriterionforParetoEfficiencyAParetoinefficientemeansthereremainunrealizedmutualgains-to-trade.Anymarketethatachievesallpossiblegains-to-trademustbeParetoefficient.ParetoEfficiencyCompetitiveequilibrium:allcloseapartmentrentersvaluethematthemarketpricepeormoreallothersvaluecloseapartmentsatlessthanpesonomutuallybeneficialtradesremainsotheeisParetoefficient.ParetoEfficiencyDiscriminatoryMonopoly:assig