曼昆经济学 宏观经济学 第五版 教师参考手册 chap06.docx

曼昆经济学 宏观经济学 第五版 教师参考手册 chap06.docx

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曼昆经济学宏观经济学第五版教师参考手册chap06

6

SUPPLY,DEMAND,ANDGOVERNMENTPOLICIES

WHAT’SNEW:

AnewIntheNewsboxhasbeenaddedon“DoesaDroughtNeedtocauseaWaterShortage?

”TheIntheNewsboxon“RentControlinNewYorkCity”hasbeenupdatedwithanewarticle.

LEARNINGOBJECTIVES:

Bytheendofthischapter,studentsshouldunderstand:

Øtheeffectsofgovernmentpoliciesthatplaceaceilingonprices.

Øtheeffectsofgovernmentpoliciesthatputafloorunderprices.

Øhowataxonagoodaffectsthepriceofthegoodandthequantitysold.

Øthattaxesleviedonbuyersandtaxesleviedonsellersareequivalent.

Øhowtheburdenofataxissplitbetweenbuyersandsellers.

KEYPOINTS:

1.Apriceceilingisalegalmaximumonthepriceofagoodorservice.Anexampleisrentcontrol.Ifthepriceceilingisbelowtheequilibriumprice,thequantitydemandedexceedsthequantitysupplied.Becauseoftheresultingshortage,sellersmustinsomewayrationthegoodorserviceamongbuyers.

2.Apricefloorisalegalminimumonthepriceofagoodorservice.Anexampleistheminimumwage.Ifthepricefloorisabovetheequilibriumprice,thequantitysuppliedexceedsthequantitydemanded.Becauseoftheresultingsurplus,buyers’demandsforthegoodorservicemustinsomewayberationedamongsellers.

3.Whenthegovernmentleviesataxonagood,theequilibriumquantityofthegoodfalls.Thatis,ataxshrinksthesizeofthemarket.

4.Ataxonagoodplacesawedgebetweenthepricepaidbybuyersandthepricereceivedbysellers.Whenthemarketmovestothenewequilibrium,buyerspaymoreforthegoodandsellersreceivelessforit.Inthissense,buyersandsellerssharethetaxburden.theincidenceofataxdoesnotdependonwhetherthetaxisleviedonbuyersorsellers.

5.Theincidenceofataxdependsonthepriceelasticitiesofsupplyanddemand.Theburdentendstofallonthesideofthemarketthatislesselasticbecausethatsideofthemarketcanrespondlesseasilytothetaxbychangingthequantityboughtorsold.

CHAPTEROUTLINE:

I.ControlsonPrices

A.DefinitionofPriceCeiling:

alegalmaximumonthepriceatwhichagoodcanbesold.

B.DefinitionofPriceFloor:

alegalminimumonthepriceatwhichagoodcanbesold.

C.HowPriceCeilingsAffectMarketOutcomes

Figure6-1

1.Therearetwopossibleoutcomesifapriceceilingisputintoplaceinamarket.

a.Ifthepriceceilingishigherthanorequaltotheequilibriumprice,itisnotbinding.

b.Ifthepriceceilingislowerthantheequilibriumprice,theceilingisabindingconstraintandashortageiscreated.

Price

Supply

PriceCeiling

Shortage

Demand

Quantity

Demanded

Quantity

Supplied

Quantity

2.Ifashortageforaproductoccurs（andpricecannotadjusttoeliminateit）,amethodforrationingthegoodmustdevelop.

3.CaseStudy:

LinesattheGasPump

Figure6-2

a.In1973,OPECraisedthepriceofcrudeoilwhichledtoareductioninthesupplyofgasoline.

b.Thefederalgovernmentputpriceceilingsintoplaceandthiscreatedlargeshortages.

c.Motoristswereforcedtospendlargeamountsoftimeinlineatthegaspump（whichishowthegaswasrationed）.

ALTERNATIVECLASSROOMEXAMPLE:

Askstudentsabouttherentalmarketintheirtown.Drawasupply-and-demandgraphfortwobedroomapartmentsaskingstudentswhattheybelievetheequilibriumrentalrateis.Thensuggestthatthecitycouncilisaccusinglandlordsoftakingadvantageofstudentsandthusplacesapriceceilingbelowtheequilibriumprice.Makesurethatstudentscanseethatashortageofapartmentswouldresult.Askstudentstoidentifythewinnersandlosersofthisgovernmentpolicy.

d.Eventually,thegovernmentrealizeditsmistakeandrepealedthepriceceiling.

4.IntheNews:

DoesaDroughtNeedtoCauseaWaterShortage?

a.Duringthesummerof1999,theEastCoastoftheU.S.experiencedashortageofwater.

b.ThisisanarticlefromtheWallStreetJournalsuggestingawayinwhichtheshortagecouldhavebeenavoided.

5.CaseStudy:

RentControlintheShortRunandtheLongRun

Figure6-3

a.Thegoalofrentcontrolistomakehousingmoreaffordableforthepoor.

b.Sincethesupplyofapartmentsisfixed（perfectlyinelastic）intheshortrunandupward-sloping（elastic）inthelongrun,theshortageismuchlargerinthelongrunthanintheshortrun.

c.Rentcontrolledapartmentsarerationedinanumberofwaysincludinglongwaitinglists,discriminationagainstminoritiesandfamilieswithchildren,andevenunder-the-tablepaymentstolandlords.

d.Thequalityofapartmentsalsosuffersduetorentcontrol.

6.IntheNews:

RentControlinNewYorkCity

a.Rentcontrolisapolicythathasfewsupporters（otherthanthoselivinginarentcontrolledapartment）.

b.ThisisanarticlefromTheNewYorkTimesdescribingthepossibilityoftheendofrentcontrolinNewYorkCity.

D.HowPriceFloorsAffectMarketOutcomes

Figure6-4

1.Therearetwopossibleoutcomesifapricefloorisputintoplaceinamarket.

a.Ifthepricefloorislowerthanorequaltotheequilibriumprice,itisnotbinding.

b.Ifthepricefloorishigherthantheequilibriumprice,thefloorisabindingconstraintandasurplusiscreated.

Price

Supply

Surplus

PriceFloor

Demand

Quantity

Supplied

Quantity

Demanded

Quantity

ALTERNATIVECLASSROOMEXAMPLE:

Gothroughanexamplewithanagriculturalpricesupport.Showstudentsthat,eventhoughapricesupportisnotalegalminimumprice,itsresultisexactlythesameasapricefloor.Makesurethatstudentscanseethatasurpluswillresult.Askstudentstoidentifythewinnersandlosersofthisgovernmentpolicy.Pointoutthecostsoftheprogram（purchasingthesurplusandstoringit）.

2.CaseStudy:

TheMinimumWage

Figure6-5

a.Themarketforlaborlookslikeanyothermarket:

downward-slopingdemand,upward-slopingsupply,equilibriumprice（calledawage）,andequilibriumquantityoflaborhired.

b.Iftheminimumwageisabovetheequilibriumwageinthelabormarket,asurplusoflaborwilldevelop（unemployment）.

c.Theminimumwagewillbeabindingconstraintonlyinmarketswhereequilibriumwagesarelow.

d.Thus,theminimumwagewillhaveitsgreatestimpactonthemarketforteenagersandotherunskilledworkers.

E.EvaluatingPriceControls

Thisisagoodchancetoreinforcetheprinciple“Marketsareusuallyagoodwaytoorganizeeconomicactivity.”

1.Becausemosteconomistsfeelthatmarketsareusuallyagoodwaytoorganizeeconomicactivity,mostopposetheuseofpriceceilingsandfloors.

2.Priceceilingsandpricefloorsoftenhurtthepeopletheyareintendedtohelp.

a.Rentcontrolscreateashortageofqualityhousingandprovidedisincentivesforbuildingmaintenance.

b.Minimumwagelawscreatehigherratesofunemploymentforteenageandlowskilledworkers.

Bepreparedtoanswerthequestion,“Ifpricecontrolshavesuchadverseconsequences,whyaretheyimposed?

”Youmaywanttopointoutthat,sometimes,economicignoranceleadstounintendedoutcomes.Youmayalsowanttopointoutthateconomicanalysisservesasonlyaguidetopolicymakers.Theymaychoosetoignoreitwhenformingpolicy.Inaddition,itisofteninterestingtoencouragethestudentstothinkaboutthedistributionaleffectsofrentcontrol.

II.Taxes

A.DefinitionofTaxIncidence:

thestudyofwhobearstheburdenoftaxation.

B.HowTaxesonBuyersAffectMarketOutcomes

UsethischancetoreinforcethethreestepslearnedinChapter4.Studentsshoulddecidewhetherthistaxlawaffectsthedemandcurveorthesupplycurve,decidewhichwayitshifts,andthenexaminehowtheshiftaffectsequilibriumpriceandquantity.

1.Ifthegovernmentrequiresthebuyertopayacertaindollaramountforeachunitofagoodpurchased,thiswillcauseadecreaseindemand.

Examplesofunittaxesincludemostgovernmentexcisetaxesonproductssuchasgasoline,alcohol,andtobacco.

Figure6-6

2.Thedemandcurvewillshiftdownbytheamountofthetax.

Youwillwanttobeverycarefulwhendiscussingthe“downward”shiftofthedemandcurvegiventhatweencouragestudentstothinkofsupplyanddemandcurvesshifting“right”and“left.”

Supply

Price

Pbuyers

Tax

Pwithouttax

Psellers

D1

D2

Quantity

3.Thequantityofthegoodsoldwilldecline.

4.Buyersandsellerswillsharetheburdenofthetax-buyerspaymoreforthegood（includingthetax）andsellersreceiveless.

C.HowTaxesonSellersAffectMarketOutcomes

Figure6-7

1.Ifthegovernmentrequiresthesellertopayacertaindollaramountforeachunitofagoodpurchased,thiswillcauseadecreaseinsupply.

2.Thesupplycurvewillshiftupbytheamountofthetax.

3.Thequantityofthegoodsoldwilldecline.

4.Buyersandsellerswillsharetheburdenofthetax-buyerspaymoreforthegoodandsellersreceiveless（becauseofthetax）.

Again,beverycarefulwhendiscussingthe“upward”shiftofthesupplycurve.Studentsoftenmistakenlybelievethatthismeansthatsupplyisincreasing.Pointouttheincreaseinthecostofsellingthegood.Ifstudentsunderstandthatanincreaseincostleadstoadecreaseinsupply,theywillbelesslikelytobecomeconfused.

S2

Price

S1

Pbuyers

Tax

Pwithouttax

Psellers

Demand

Quantity

Stressthattheoutcomeofataxleviedonsellersisexactlythesameastheoutcomeofataxleviedonbuyers.Whendrawingthisinclass,makesurethatthepricethatbuyersenduppayingandthepricethatsellersendupreceivingisthesameinbothexamples.

D.CaseStudy:

CanCongressDistributetheBurdenofaPayrollTax?

F