清华大学中级微观经济学讲义15课件

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1、http://www.sem.tsinghua.edu.cn/ChapterFifteenMarketDemandWhatIsthePurposeofThisChapter?Weaggregateindividualdemandandformamarketdemandfunction.WestudyapropertyofthemarketdemandfunctionFromIndividualtoMarketDemandFunctionsThinkofaneconomycontainingnconsumers,denote

2、dbyi=1,…,n.Consumeri’sordinarydemandfunctionforcommodityjisFromIndividualtoMarketDemandFunctionsWhenallconsumersareprice-takers,themarketdemandfunctionforcommodityjisFromIndividualtoMarketDemandFunctionsp1p1p1201535p1’p1”p1’p1”p1’p1”The“horizontalsum”ofthedemandc

3、urvesofindividualsAandB.AnImportantConcept:ElasticityElasticitymeasuresthe“sensitivity”ofonevariablewithrespecttoanother.TheelasticityofvariableXwithrespecttovariableYisSlopeVs.ElasticityQ:Whynotjustusetheslopeofademandcurvetomeasurethesensitivityofquantitydemand

4、edtoachangeinacommodity’sownprice?A:Becausethevalueofsensitivitythendependsuponthe(arbitrary)unitsofmeasurementusedforquantitydemanded.ArcandPointElasticitiesAn“average”own-priceelasticityofdemandforcommodityioveranintervalofvaluesforpiisanarc-elasticity,usuallyco

5、mputedbyamid-pointformula.Elasticitycomputedforasinglevalueofpiisapointelasticity.PointOwn-PriceElasticitypiXi*pi’Whatistheown-priceelasticityofdemandinaverysmallintervalofpricescenteredonpi’?istheelasticityatthepointPointOwn-PriceElasticityE.g.Supposepi=a-bXi.

6、ThenXi=(a-pi)/bandTherefore,PointOwn-PriceElasticitypiXi*api=a-bXi*a/ba/2a/2bown-priceelasticown-priceinelastic(own-priceunitelastic)PointOwn-PriceElasticityE.g.ThensoPointOwn-PriceElasticitypiXi*everywherealongthedemandcurve.RevenueandOwn-PriceElasticityofDemand

7、Sellers’revenueisSoRevenueandOwn-PriceElasticityofDemandsoifthenandachangetopricedoesnotaltersellers’revenue.RevenueandOwn-PriceElasticityofDemandbutifthenandapriceincreaseraisessellers’revenue.RevenueandOwn-PriceElasticityofDemandAndifthenandapriceincreasereduc

8、essellers’revenue.MarginalRevenueandOwn-PriceElasticityofDemandAseller’smarginalrevenueistherateatwhichrevenuechangeswiththenumberofunitssoldbytheselle