经济学第五章

Supply,Demand,and

GovernmentPolicies6供给、需求与政府政策Inthischapter,

lookfortheanswerstothesequestions:Whatarepriceceilingsandpricefloors?

Whataresomeexamplesofeach?Howdopriceceilingsandpricefloorsaffectmarketoutcomes?Howdotaxesaffectmarketoutcomes?

Howdotheeffectsdependonwhether

thetaxisimposedonbuyersorsellers?Whatistheincidenceofatax?

Whatdeterminestheincidence?1什么是价格上限与价格下限？各有什么例子？价格上限与价格下限如何影响市场结果？

税收如何影响市场结果？对买者还是卖者征税对市场结果有什么不同吗？什么是税收归宿？什么决定税收归宿？1SUPPLY,DEMAND,ANDGOVERNMENTPOLICIESGovernmentPoliciesThatAlterthe

PrivateMarketOutcome

PricecontrolsPriceceiling:alegalmaximumontheprice

ofagoodorserviceExample:rentcontrol

Pricefloor:alegalminimumonthepriceof

agoodorserviceExample:minimumwage

TaxesThegovtcanmakebuyersorsellerspayaspecificamountoneachunitbought/sold.Wewillusethesupply/demandmodeltosee

howeachpolicyaffectsthemarketoutcome

(thepricebuyerspay,thepricesellersreceive,andeq’mquantity).价格控制：价格上限：出售一种物品或服务的法定最高价格比如：租金控制价格下限：出售一种物品或服务的法定最低价格

税收：政府要求买者或卖者每买进或卖出一单位物品所支付的一定数量的货币2SUPPLY,DEMAND,ANDGOVERNMENTPOLICIESEXAMPLE1:TheMarketforApartmentsEq’mw/o

pricecontrolsPQDSRentalpriceofapts$800300Quantityofapartments没有价格控制的均衡3SUPPLY,DEMAND,ANDGOVERNMENTPOLICIESHowPriceCeilingsAffectMarketOutcomesApriceceiling

abovethe

eq’mpriceis

notbinding–

hasnoeffect

onthemarketoutcome.价格上限高于均衡均衡价格时没有限制性—即对市场结果没有影响

PQDS$800300Price

ceiling$10004SUPPLY,DEMAND,ANDGOVERNMENTPOLICIESHowPriceCeilingsAffectMarketOutcomesTheeq’mprice($800)isabovetheceilingandthereforeillegal.违法的Theceiling

isabindingconstraint

ontheprice,causesashortage.PQDS$800Price

ceiling$500250400shortage5SUPPLY,DEMAND,ANDGOVERNMENTPOLICIESHowPriceCeilingsAffectMarketOutcomesInthelongrun,supplyanddemand

aremore

price-elastic.So,theshortage

islarger.长期，供给与需求都更具有弹性。因此，短期更加严重PQDS$800150Price

ceiling$500450shortage6SUPPLY,DEMAND,ANDGOVERNMENTPOLICIESShortagesandRationing短缺与配给Withashortage,sellersmustrationthegoodsamongbuyers.Somerationingmechanisms:(1)Longlines

(2)Discriminationaccordingtosellers’biasesThesemechanismsareoftenunfair,andinefficient:thegoodsdonotnecessarilygotothebuyerswhovaluethemmosthighly.Incontrast,whenpricesarenotcontrolled,

therationingmechanismisefficient(thegoods

gotothebuyersthatvaluethemmosthighly)

andimpersonal(andthusfair).面临短缺时，卖者必须在买者之间配给稀缺物品

配给机制：（1）排长队（2）根据卖者的偏好这些配件机制既可能是不公平的，也是无效率的：因为物品并不一定会卖给对它评价最高的买者与此相比，一个自由竞争市场中的配给机制既有效率（物品卖给对它评价最高的买者），也是客观的（就是公平的）7SUPPLY,DEMAND,ANDGOVERNMENTPOLICIESEXAMPLE2:TheMarketforUnskilledLaborEq’mw/o

pricecontrolsWLDSWagepaidtounskilledworkers$4500Quantityofunskilledworkers8SUPPLY,DEMAND,ANDGOVERNMENTPOLICIESHowPriceFloorsAffectMarketOutcomesWLDS$4500Price

floor$3Apricefloor

belowthe

eq’mpriceis

notbinding–

hasnoeffect

onthemarketoutcome.低于均衡价格的的价格下限没有限制性—即对市场结果没有影响9SUPPLY,DEMAND,ANDGOVERNMENTPOLICIESHowPriceFloorsAffectMarketOutcomesWLDS$4Price

floor$5Theeq’mwage($4)isbelowthefloorandtherefore

illegal.Thefloor

isabindingconstraint

onthewage,

causesa

surplus(i.e.,unemployment).400550laborsurplus均衡价格（$4）低于价格下限，因此是违法的价格下限是一种限制性约束，引起了过剩（也就是失业10SUPPLY,DEMAND,ANDGOVERNMENTPOLICIESMinwagelaws

donotaffect

highlyskilledworkers.Theydoaffectteenworkers.Studies:

A10%increase

intheminwageraisesteenunemployment

by1-3%.TheMinimumWageWLDS$4Min.wage$5400550unemp-loyment最低工资法对技能高的工人并没有影响，它们影响的是青少年研究表明：最低工资每上升10%，就会使青少年就业减少1-3%。11SUPPLY,DEMAND,ANDGOVERNMENTPOLICIESACTIVELEARNING1

PricecontrolsQPS0Themarketfor

hotelroomsDDetermine

effectsof:A.

$90price

ceilingB. $90price

floorC. $120price

floor1212SUPPLY,DEMAND,ANDGOVERNMENTPOLICIESACTIVELEARNING1

A.$90priceceilingQPS0Themarketfor

hotelroomsDThepricefallsto$90.Buyersdemand

120rooms,sellerssupply90,leavingashortage.shortage=30Priceceiling1313SUPPLY,DEMAND,ANDGOVERNMENTPOLICIESACTIVELEARNING1

B.$90pricefloorQPS0Themarketfor

hotelroomsDEq’mpriceisabovethefloor,sofloorisnotbinding.P=$100,

Q=100rooms.Pricefloor1414SUPPLY,DEMAND,ANDGOVERNMENTPOLICIESACTIVELEARNING1

C.$120pricefloorQPS0Themarketfor

hotelroomsDTheprice

risesto$120.Buyers

demand

60rooms,

sellerssupply120,causingasurplus.surplus=60Pricefloor1515SUPPLY,DEMAND,ANDGOVERNMENTPOLICIESEvaluatingPriceControlsRecalloneoftheTenPrinciplesfromChapter1:

Marketsareusuallyagoodway

toorganizeeconomicactivity.

Pricesarethesignalsthatguidetheallocationofsociety’sresources.Thisallocationisalteredwhenpolicymakersrestrictprices.Pricecontrolsoftenintendedtohelpthepoor,

butoftenhurtmorethanhelp.价格是指引社会资源配置的信号。当政府进行价格控制时，这种配置通常会发生变化价格控制想帮助穷人，但往往却伤害了那些它本想帮助的人16SUPPLY,DEMAND,ANDGOVERNMENTPOLICIESTaxesThegovtleviestaxesonmanygoods&servicestoraiserevenuetopayfornationaldefense,publicschools,etc.Thegovtcanmakebuyersorsellerspaythetax.Thetaxcanbea%ofthegood’sprice,

oraspecificamountforeachunitsold.Forsimplicity,weanalyzeper-unittaxesonly.政府对许多物品与劳务征税是为了给国防，公立学校等这类公共项目筹资政府能想买者或卖者征税税收可以是物品价格的一个比例或者每售出一单位物品需支付一定数量的货币简化起见，我们仅分析后者17SUPPLY,DEMAND,ANDGOVERNMENTPOLICIESS1EXAMPLE3:TheMarketforPizzaEq’m

w/otaxPQD1$10.0050018SUPPLY,DEMAND,ANDGOVERNMENTPOLICIESS1D1$10.00500ATaxonBuyersThepricebuyerspay

isnow$1.50higherthanthemarketpriceP.Pwouldhavetofall

by$1.50tomake

buyerswilling

tobuysameQ

asbefore.E.g.,ifPfalls

from$10.00to$8.50,

buyersstillwillingto

purchase500pizzas.PQD2Effectsofa$1.50perunittaxonbuyers$8.50Hence,ataxonbuyersshiftstheDcurvedownbytheamountofthetax.Tax19SUPPLY,DEMAND,ANDGOVERNMENTPOLICIESS1D1$10.00500ATaxonBuyersPQD2$11.00PB=$9.50PS=TaxEffectsofa$1.50perunittaxonbuyersNeweq’m:新均衡Q=450Sellers

receive

PS=$9.50Buyerspay

PB=$11.00Differencebetweenthem

=$1.50=tax45020SUPPLY,DEMAND,ANDGOVERNMENTPOLICIES450S1TheIncidenceofaTax:税收归宿howtheburdenofataxissharedamong

marketparticipants税收负担在市场参与者之间进行分配的方式PQD1$10.00500D2$11.00PB=$9.50PS=TaxInourexample,buyerspay

$1.00more,sellersget

$0.50less.21SUPPLY,DEMAND,ANDGOVERNMENTPOLICIESS1ATaxonSellersPQD1$10.00500S2Effectsofa$1.50perunittaxonsellersThetaxeffectivelyraisessellers’costsby

$1.50perpizza.Sellerswillsupply

500pizzas

onlyif

Prisesto$11.50,

tocompensatefor

thiscostincrease.$11.50Hence,ataxonsellersshiftsthe

Scurveupbytheamountofthetax.因此，对卖者征税使供给曲线向上移动，移动幅度为税收量Tax22SUPPLY,DEMAND,ANDGOVERNMENTPOLICIESS1ATaxonSellersPQD1$10.00500S2450$11.00PB=$9.50PS=TaxEffectsofa$1.50perunittaxonsellersNeweq’m:Q=450Buyerspay

PB=$11.00Sellers

receive

PS=$9.50Differencebetweenthem

=$1.50=tax23SUPPLY,DEMAND,ANDGOVERNMENTPOLICIESS1TheOutcomeIstheSameinBothCases!Whatmattersisthis:Ataxdrives

awedgebetweenthepricebuyerspayandthepricesellersreceive.PQD1$10.00500450$9.50$11.00PB=PS=TaxTheeffectsonPandQ,andthetaxincidencearethesamewhetherthetaxisimposedonbuyersorsellers!在这两种情况下：税收都在买者支付的价格和卖者得到的价格之间打入了一个契子24SUPPLY,DEMAND,ANDGOVERNMENTPOLICIESACTIVELEARNING2

EffectsofataxQPS0Themarketfor

hotelroomsDSupposegovtimposesataxonbuyersof$30perroom.Findnew

Q,PB,PS,

andincidenceoftax.25SUPPLY,DEMAND,ANDGOVERNMENTPOLICIESACTIVELEARNING2

AnswersQPS0Themarketfor

hotelroomsDQ=80PB=$110PS=$80Incidencebuyers:$10sellers:$20TaxPB=PS=26SUPPLY,DEMAND,ANDGOVERNMENTPOLICIESElasticityandTaxIncidenceCASE1:SupplyismoreelasticthandemandPQDSTaxBuyers’shareoftaxburdenSellers’shareoftaxburdenPriceifnotaxPBPSIt’seasier

forsellersthanbuyerstoleavethemarket.Sobuyersbearmostoftheburden

ofthetax.27SUPPLY,DEMAND,ANDGOVERNMENTPOLICIESElasticityandTaxIncidenceCASE2:DemandismoreelasticthansupplyPQDSTaxBuyers’shareoftaxburdenSellers’shareoftaxburdenPriceifnotaxPBPSIt’seasierforbuyersthansellerstoleavethemarket.Sellersbearmostoftheburdenof

thetax.28SUPPLY,DEMAND,ANDGOVERNMENTPOLICIESCASESTUDY:WhoPaystheLuxuryTax?1990:Congressadoptedaluxurytaxonyachts,privateairplanes,furs,expensivecars,etc.Goalofthetax:raiserevenuefromthose

whocouldmosteasilyaffordtopay–

wealthyconsumers.Butwhoreallypaysthistax?在1990年，国会通过了一项针对游艇，私人飞机，皮衣，珠宝和豪华轿车这类物品的新的奢侈品税税收的目的；增加富人的税收但真正支付税收的人士谁？29SUPPLY,DEMAND,ANDGOVERNMENTPOLICIESCASESTUDY:WhoPaystheLuxuryTax?ThemarketforyachtsPQDSTaxBuyers’shareoftaxburdenSellers’shareoftaxburdenPBPSDemandis

price-elastic.Intheshortrun,supplyisinelastic.Hence,

companiesthatbuildyachtspaymostof

thetax.30SUPPLY,DEMAND,ANDGOVERNMENTPOLICIESCONCLUSION:GovernmentPoliciesandtheAllocationofResources结论：政府政策与资源的配置Eachofthepoliciesinthischapteraffectstheallocationofsociety’sresources.Example1:Ataxonpizzareduceseq’mQ. Withlessproductionofpizza,resources(workers,ovens,cheese)willbecomeavailabletootherindustries.Example2:Abindingminimumwagecauses

asurplusofworkers,awasteofresources.So,it’simportantforpolicymakerstoapplysuchpoliciesverycarefully.本章的两种政策都会影响社会资源的配置：

例1：对皮萨的征税降低了均衡数量。当皮萨的产量降低时，资源（工人，烤箱，奶酪）将会转移到其它行业例2：一个限制性的最低工资会引起工人的超额供给，这是对资源的浪费因此，决策者在应用这些政策时需要非常小心31SUPPLY,DEMAND,ANDGOVERNMENTPOLICIESCHAPTERSUMMARYApriceceil