中微课件范里安版 Micro Ch15.ppt

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1、ChapterFifteenMarketDemandWhatIsthePurposeofThisChapter?Weaggregateindividualdemandandformamarketdemandfunction.WestudyapropertyofthemarketdemandfunctionFromIndividualtoMarketDemandFunctionsThinkofaneconomycontainingnconsumers,denotedbyi=1,…,n.Consumeri’sordinarydemandfunctionforcommodityjisF

2、romIndividualtoMarketDemandFunctionsWhenallconsumersareprice-takers,themarketdemandfunctionforcommodityjisFromIndividualtoMarketDemandFunctionsp1p1p1201535p1’p1”p1’p1”p1’p1”The“horizontalsum”ofthedemandcurvesofindividualsAandB.AnImportantConcept:ElasticityElasticitymeasuresthe“sensitivity”o

3、fonevariablewithrespecttoanother.TheelasticityofvariableXwithrespecttovariableYisSlopeVs.ElasticityQ:Whynotjustusetheslopeofademandcurvetomeasurethesensitivityofquantitydemandedtoachangeinacommodity’sownprice?A:Becausethevalueofsensitivitythendependsuponthe(arbitrary)unitsofmeasurementusedfor

4、quantitydemanded.ArcandPointElasticitiesAn“average”own-priceelasticityofdemandforcommodityioveranintervalofvaluesforpiisanarc-elasticity,usuallycomputedbyamid-pointformula.Elasticitycomputedforasinglevalueofpiisapointelasticity.PointOwn-PriceElasticitypiXi*pi’Whatistheown-priceelasticityofde

5、mandinaverysmallintervalofpricescenteredonpi’?istheelasticityatthepointPointOwn-PriceElasticityE.g.Supposepi=a-bXi.ThenXi=(a-pi)/bandTherefore,PointOwn-PriceElasticitypiXi*api=a-bXi*a/ba/2a/2bown-priceelasticown-priceinelastic(own-priceunitelastic)PointOwn-PriceElasticityE.g.ThensoPointOwn-

6、PriceElasticitypiXi*everywherealongthedemandcurve.RevenueandOwn-PriceElasticityofDemandSellers’revenueisSoRevenueandOwn-PriceElasticityofDemandsoifthenandachangetopricedoesnotaltersellers’revenue.RevenueandOwn-PriceElasticityofDemandbutifthenandapriceincreaseraisessellers’revenue.Revenuean

7、dOwn-PriceElasticityofDemandAndifthenandapriceincreasereducessellers’revenue.MarginalRevenueandOwn-PriceElasticityofDemandAseller’smarginalrevenueistherateatwhichrevenuechangeswiththenumberofunitssoldbytheseller.MarginalRevenueandOwn-PriceEl