供给、需求与政府政策

供给、、需求求与政政府政政策供给、、需求求与政政府政政策在一个个没有有政府府管制制的竞竞争市市场上上，市市场力力量调调整均均衡价价格、、均衡衡数量量.并非每每个人人对这这种自自由市市场调调整过过程的的结果果都感感到满满意.经济学学家的的作用用之一一便是是运用用他们们的理理论帮帮助世世界更更好.价格控控制政策制制定者者认为为一种种物品品或劳劳务的的市场场价格格对买买者或或卖者者不公公平时时所实实施的的.政府定定出的的价格格上限限和价价格下下限.价格控控制价格上上限（（PriceCeiling）可以出出售一一种物物品的的法定定最高高价格格.价格下下限（（PriceFloor）可以出出售一一种物物品的的法定定最低低价格格.价格上上限如如何影影响市市场结结果政府实实现价价格上上限时时可能能有两两种结结果:价格上上限高高于均均衡价价格，，价格格上限限没有有限制制作用用.价格上上限低低于于于均衡衡价格格，价价格上上限有有限制制性约约束.Figure1AMarketwithaPriceCeiling(a)APriceCeilingThatIsNotBindingQuantityofIce-CreamCones0PriceofIce-CreamConeEquilibriumquantity$4PriceceilingEquilibriumpriceDemandSupply3100Figure1AMarketwithaPriceCeilingCopyright©2003Southwestern/ThomsonLearning(b)APriceCeilingThatIsBindingQuantityofIce-CreamCones0PriceofIce-CreamConeDemandSupply2PriceceilingShortage75Quantitysupplied125QuantitydemandedEquilibriumprice$3价格上上限如如何影影响市市场结结果价格上上限的的结果果有限制制作用用的价价格上上限导导致QD>QS，带来短短缺.比如：：计划划经济济的各各种票票证非价格格配给给机制制比如:排排长长队，，卖者者歧视视第一，，经济济学家家几乎乎一致致认为为对市市场干干预具具有某某种必必要性性。第二，，经济济学家家认为为应当当注意意对供供求规规律作作用干干预不不同方方式选选择。。区分两类干干预方式：：一种是取消消市场机制制的干预方方式另一种是与与供求规律律具有兼容容性的干预预方式1973,OPEC提高了世界界石油市场场的原油价价格.由由于原油是是用于生产产汽油的主主要投入,较高的的石油价格格减少了汽汽油供给.什么导致了了人们排队队加油呢?案例:加油油站前的长长队经济学家认认为政府的的价格管制制要为美国国人排队等等候买汽油油而失去的的许多时间间承担部分分责任.Figure2TheMarketforGasolinewithaPriceCeilingCopyright©2003Southwestern/ThomsonLearning(a)ThePriceCeilingonGasolineIsNotBindingQuantityofGasoline0PriceofGasoline1.Initially,thepriceceilingisnotbinding...PriceceilingDemandSupply,S1P1Q1Figure2TheMarketforGasolinewithaPriceCeilingCopyright©2003Southwestern/ThomsonLearning(b)ThePriceCeilingonGasolineIsBindingQuantityofGasoline0PriceofGasolineDemandS1S2PriceceilingQS4....resultinginashortage.3....thepriceceilingbecomesbinding...2....butwhensupplyfalls...P2QDP1Q1案例研究究:短期与长长期租金金控制租金控制制是地方方政府规规定房东东向房东东收取的的租金上上限该政策的的目的是是帮助穷穷人更能能租得起起住房.一位经济济学家称称租金控控制是““除了了轰炸之之外，毁毁灭一个个城市的的最好方方法.””Figure3RentControlintheShortRunandintheLongRunCopyright©©2003Southwestern/ThomsonLearning(a)RentControlintheShortRun(supplyanddemandareinelastic)QuantityofApartments0SupplyControlledrentRentalPriceofApartmentDemandShortageFigure3RentControlintheShortRunandintheLongRunCopyright©©2003Southwestern/ThomsonLearning(b)RentControlintheLongRun(supplyanddemandareelastic)0RentalPriceofApartmentQuantityofApartmentsDemandSupplyControlledrentShortage价格下限限如何影影响市场场结果政府实行行价格下下限时，，可能有有两种结结果.均衡价格格高于价价格下限限，价格格下限没没有限制制性.均衡价格格低于价价格下限限，价格格下限有有限制性性，引起起过剩.Figure4AMarketwithaPriceFloorCopyright©©2003Southwestern/ThomsonLearning(a)APriceFloorThatIsNotBindingQuantityofIce-CreamCones0PriceofIce-CreamConeEquilibriumquantity2PricefloorEquilibriumpriceDemandSupply$3100Figure4AMarketwithaPriceFloorCopyright©©2003Southwestern/ThomsonLearning(b)APriceFloorThatIsBindingQuantityofIce-CreamCones0PriceofIce-CreamConeDemandSupply$4Pricefloor80Quantitydemanded120QuantitysuppliedEquilibriumpriceSurplus3价格下限限如何影影响市场场结果价格下限限阻止供供求力量量使价格格向均衡衡价格变变动.当市场价格达达到下限时，，就不能再下下降了，此时时的市场价格格等于价格下下限.价格下限如何何影响市场结结果有限制性的价价格下限会导导致...QS>QD，引起过剩.非价格机制用用歧视标准等等代替价格机机制作为配给给机制.比如:最低低工作，农业业价格支持最低工资价格下限的一一个重要例子子是最低工资资。最低工资资法规定了任任何一个雇主主要支付的最最低劳动力价价格。Figure5HowtheMinimumWageAffectstheLaborMarketCopyright©2003Southwestern/ThomsonLearningQuantityofLaborWage0LabordemandLaborSupplyEquilibriumemploymentEquilibriumwageFigure5HowtheMinimumWageAffectstheLaborMarketCopyright©2003Southwestern/ThomsonLearningQuantityofLaborWage0LaborSupplyLaborsurplus(unemployment)LabordemandMinimumwageQuantitydemandedQuantitysupplied税收政府用税收为为公共项目筹筹资.税收归宿税收归宿（Taxincidence）：如何在市场场参与者间分分担税收负担担Figure6ATaxonBuyersCopyright©2003Southwestern/ThomsonLearningQuantityofIce-CreamCones0PriceofIce-CreamConePricewithouttaxPricesellersreceiveEquilibriumwithouttaxTax($0.50)PricebuyerspayD1D2Supply,S1Ataxonbuyersshiftsthedemandcurvedownwardbythesizeofthetax($0.50).$3.3090Equilibriumwithtax2.803.00100向买者（和卖卖者）征税如如何影响市场场结果税收抑制了市市场活动.当对一种物品品征税时，该该物品在新均均衡时的销售售量减少了.买者与卖者分分摊税收负担担.Figure7ATaxonSellersCopyright©2003Southwestern/ThomsonLearning2.80QuantityofIce-CreamCones0PriceofIce-CreamConePricewithouttaxPricesellersreceiveEquilibriumwithtaxEquilibriumwithouttaxTax($0.50)PricebuyerspayS1S2Demand,D1Ataxonsellersshiftsthesupplycurveupwardbytheamountofthetax($0.50).3.00100$3.3090对买者征税和和卖者征税是是相同的Figure8工薪税Copyright©2003Southwestern/ThomsonLearningQuantityofLabor0Wage

LabordemandLaborsupply税收楔子WageworkersreceiveWagefirmspayWagewithouttax弹性与税收归归宿税收归宿是关于谁来承担担税收负担的的研究.税收导致市场场均衡的变化化.无论对谁征税税，买者与卖卖者分摊税收收负担.弹性与税收归归宿税收负担如何何划分?答案取决于需需求和供给的的相对弹性.Figure9HowtheBurdenofaTaxIsDividedCopyright©2003Southwestern/ThomsonLearningQuantity0PriceDemandSupplyTaxPricesellersreceivePricebuyerspay(a)ElasticSupply,InelasticDemand2....theincidenceofthetaxfallsmoreheavilyonconsumers...1.Whensupplyismoreelasticthandemand...Pricewithouttax3....thanonproducers.Figure9HowtheBurdenofaTaxIsDividedCopyright©2003Southwestern/ThomsonLearningQuantity0PriceDemandSupplyTaxPricesellersreceivePricebuyerspay(b)InelasticSupply,ElasticDemand3....thanonconsumers.1.Whendemandismoreelasticthansupply...Pricewithouttax2....theincidenceofthetaxfallsmoreheavilyonproducers...税收负担如何何划分?税收负担更多多地落在缺乏乏弹性的市场场一方身上.ELASTICITYANDTAXINCIDENCESummaryPricecontrolsincludepriceceilingsandpricefloors.A