曼昆经济学 宏观经济学 第五版 教师参考手册 chap07.docx

曼昆经济学 宏观经济学 第五版 教师参考手册 chap07.docx

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曼昆经济学宏观经济学第五版教师参考手册chap07

7

CONSUMERS,PRODUCERS,ANDEFFICIENCYOFMARKETS

WHAT’SNEW:

TheFYIboxon“AdamSmithandtheInvisibleHand”hasbeenmovedtoChapter1.

LEARNINGOBJECTIVES:

Bytheendofthischapter,studentsshouldunderstand:

Øthelinkbetweenbuyers’willingnesstopayforagoodandthedemandcurve.

Øhowtodefineandmeasureconsumersurplus.

Øthelinkbetweensellers’costsofproducingagoodandthesupplycurve.

Øhowtodefineandmeasureproducersurplus.

Øthattheequilibriumofsupplyanddemandmaximizestotalsurplusinamarket.

KEYPOINTS:

1.Consumersurplusequalsbuyers’willingnesstopayforagoodminustheamounttheyactuallypayforit,anditmeasuresthebenefitbuyersgetfromparticipatinginamarket.Consumersurpluscanbecomputedbyfindingtheareabelowthedemandcurveandabovetheprice.

2.Producersurplusequalstheamountsellersreceivefortheirgoodsminustheircostsofproduction,anditmeasuresthebenefitsellersgetfromparticipatinginamarket.Producersurpluscanbecomputedbyfindingtheareabelowthepriceandabovethesupplycurve.

3.Anallocationofresourcesthatmaximizesthesumofconsumerandproducersurplusissaidtobeefficient.Policymakersareoftenconcernedwiththeefficiency,aswellastheequity,ofeconomicoutcomes.

4.Theequilibriumofsupplyanddemandmaximizesthesumofconsumerandproducersurplus.Thatis,theinvisiblehandofthemarketplaceleadsbuyersandsellerstoallocateresourcesefficiently.

5.Marketsdonotallocateresourcesefficientlyinthepresenceofmarketfailuressuchasmarketpowerorexternalities.

CHAPTEROUTLINE:

I.DefinitionofWelfareEconomics:

thestudyofhowtheallocationofresourcesaffectseconomicwell-being.

Studentsoftenareconfusedbytheterm“welfareeconomics.”Remindthemthatwearetalkingaboutwell-beingandnotpublicassistance.

II.ConsumerSurplus

A.WillingnesstoPay

1.DefinitionofWillingnesstoPay:

themaximumamountthatabuyerwillpayforagood.

2.Example:

youareauctioningamint-conditionrecordingofElvisPresley’sfirstalbum.Fourbuyersshowup.Theirwillingnesstopayisasfollows:

StudentswillunderstandconsumersurplusifyoutakethetimetoworkthroughtheElvisPresleyexample.Ifyoustartwiththissimpleexample,studentswillhavenotroubleunderstandinghowtofindconsumersurplusonagraph.

Table7-1

Buyer

WillingnesstoPay

John

$100

Paul

80

George

70

Ringo

50

Ifthebiddinggoestoslightlyhigherthan$80,allbuyersdropoutexceptforJohn.SinceJohniswillingtopaymorethanhehastoforthealbum,hederivessomebenefitfromparticipatinginthemarket.

3.DefinitionofConsumerSurplus:

abuyer’swillingnesstopayminustheamountthebuyeractuallypays.

4.Notethatifyouhadmorethanonecopyofthealbum,thepriceintheauctionwouldendupbeinglower（alittleover$70inthecaseoftwoalbums）andbothJohnandPaulwouldgainconsumersurplus.

B.UsingtheDemandCurvetoMeasureConsumerSurplus

1.WecanusetheinformationonwillingnesstopaytoderiveademandcurvefortherareElvisPresleyalbum.

Table7-2

Price

Buyers

QuantityDemanded

Morethan$100

None

0

$80to$100

John

1

$70to$80

John,Paul

2

$50to$70

John,Paul,George

3

$50orless

John,Paul,George,Ringo

4

Figure7-1

Price

100

80

70

50

4

3

2

1

Quantity

2.Atanygivenquantity,thepricegivenbythedemandcurvereflectsthewillingnesstopayofthemarginalbuyer.Becausethedemandcurveshowsthebuyers’willingnesstopay,wecanusethedemandcurvetomeasureconsumersurplus.

Figure7-2

3.Consumersurpluscanbemeasuredastheareabelowthedemandcurveandabovetheprice.

C.HowaLowerPriceRaisesConsumerSurplus

Figure7-3

1.Aspricefalls,consumersurplusincreasesfortworeasons.

a.Thosealreadybuyingtheproductwillreceiveadditionalconsumersurplusbecausetheyarepayinglessfortheproductthanbefore（areaAongraph）.

b.Sincethepriceisnowlower,somenewbuyerswillenterthemarketandreceiveconsumersurplusontheseadditionalunitsofoutputpurchased（areaBongraph）.

Price

P1

A

B

P2

Demand

Q2

Q1

Quantity

D.WhatDoesConsumerSurplusMeasure?

Itisimportanttostressthatconsumersurplusismeasuredinmonetaryterms.Consumersurplusgivesusawaytoplaceamonetarycostoninefficientmarketoutcomes（duetogovernmentinvolvementormarketfailure）.

1.Rememberthatconsumersurplusisthedifferencebetweentheamountthatbuyersarewillingtopayforagoodandthepricethattheyactuallypay.

2.Thus,itmeasurestheactualbenefitthatconsumersreceivefromthegoodaboveandbeyonditscost.

ALTERNATIVECLASSROOMEXAMPLE:

ReviewthematerialonpriceceilingsfromChapter6.Redrawthemarketfortwo-bedroomapartmentsinyourtown.Drawinapriceceilingbelowtheequilibriumprice.

Thengothrough:

▪consumersurplusbeforethepriceceilingisputinplace

▪consumersurplusafterthepriceceilingisputinplace

III.ProducerSurplus

A.CostandtheWillingnesstoSell

1.DefinitionofCost:

thevalueofeverythingasellermustgiveuptoproduceagood.

Youwillneedtotakesometimeexplainingtherelationshipbetweentheproducers’willingnesstosellandthecostofproducingthegood.Therelationshipbetweencostandthesupplycurveisnotasapparentastherelationshipbetweenthedemandcurveandwillingnesstopay.

2.Example:

youwanttohiresomeonetopaintyourhouse.Therearefoursellersfromwhomyouacceptbidsforthework.Eachpainteriswillingtoworkifthepriceyouwillpayexceedsheropportunitycost.（Notethatthisopportunitycostthusrepresentswillingnesstosell.）Thecostsare:

Seller

Cost

Mary

$900

Frida

800

Georgia

600

Grandma

500

Table7-3

Biddingwillstopwhenthepricegetstobeslightlybelow$600.AllsellerswilldropoutexceptforGrandma.SinceGrandmareceivesmorethanshewouldrequiretopaintthehouse,shederivessomebenefitfromproducinginthemarket.

3.DefinitionofProducerSurplus:

theamountasellerispaidforagoodminustheseller’scost.

4.Notethatifyouhadmorethanonehousetopaint,thepriceintheauctionwouldendupbeinghigher（alittleunder$800inthecaseoftwohouses）andbothGrandmaandGeorgiawouldgainproducersurplus.

B.UsingtheSupplyCurvetoMeasureProducerSurplus

1.Wecanusetheinformationoncost（willingnesstosell）toderiveasupplycurveforhousepaintingservices.

Table7-4

Price

Sellers

QuantitySupplied

$900ormore

Mary,Frida,Georgia,Grandma

4

$800to$900

Frida,Georgia,Grandma

3

$600to$800

Georgia,Grandma

2

$500to$600

Grandma

1

lessthan$500

None

0

2.Atanygivenquantity,thepricegivenbythesupplycurverepresentsthecostofthemarginalseller.Becausethesupplycurveshowsthesellers’cost（willingnesstosell）,wecanusethesupplycurvetomeasureproducersurplus.

Figure7-4

Price

900

800

600

500

4

3

2

1

Quantity

Figure7-5

3.Producersurpluscanbemeasuredastheareaabovethesupplycurveandbelowtheprice.

C.HowaHigherPriceRaisesProducerSurplus

Figure7-6

1.Aspricerises,producersurplusincreasesfortworeasons.

a.Thosealreadysellingtheproductwillreceiveadditionalproducersurplusbecausetheyarereceivingmorefortheproductthanbefore（areaConthegraph）.

Supply

P1

Price

D

C

P2

Q2

Q1

Quantity

b.Sincethepriceisnowhigher,somenewsellerswillenterthemarketandreceiveproducersurplusontheseadditionalunitsofoutputsold（areaDonthegraph）.

ALTERNATIVECLASSROOMEXAMPLE:

ReviewthematerialonpricefloorsfromChapter6.Redrawthemarketforanagriculturalproductsuchascorn.Drawinapricesupportabovetheequilibriumprice.

Thengothrough:

▪producersurplusbeforethepricesupportisputinplace.

▪producersurplusafterthepricesupportisputinplace.

D.Producersurplusisusedtomeasureeconomicwell-beingofproducers,muchlikeconsumersurplusisusedtomeasuretheeconomicwell-beingofconsumers.

IV.MarketEfficiency

A.TheBenevolentSocialPlanner

1.Theeconomicwell-beingofeveryoneinsocietycanbemeasuredbytotalsurplus,whichisthesumofconsumersurplusandproducersurplus:

TotalSurplus=ConsumerSurplus+ProducerSurplus

TotalSurplus=（ValuetoBuyers-AmountPaidbyBuyers）+

（AmountReceivedbySellers-CostsofSellers）

BecausetheAmountPaidByBuyers=AmountReceivedBy

Sellers:

2.DefinitionofEfficiency:

thepropertyofaresourceallocationofmaximizingthetotalsurplusreceivedbyallmembersofsociety.

3.DefinitionofEquity:

thefairnessofthedistributionofwell-beingamongthemembersofsociety.

Nowmightbeagoodtimetopointoutthatmanygovernmentpoliciesinvolveatradeoffbetweenefficiencyandequity.Then,whenyouevaluategovernmentpolicies,likepriceceilingsorfloors,youcanexplainthemintermsofequityandefficiency.

B.EvaluatingtheMarketEquilibrium

Figure7-7

Supply

Price

CS

P*

PS

Demand

Q*

Quantity

1.Atthemarketequilibriumprice:

a.Buyerswhovaluetheproductmorethantheequilibriumpricewillpurchasetheproduct;thosewhodonotwillnotpurchasetheproduct.

b.Sellerswhosecostsarelessthantheequilibriumpricewillproducetheproduct;thosewhosecostsarehigherwillnotproducetheproduct.

2.Totalsurplusismaximizedatthemarketequilibrium.

Figure7-8

Supply

Price

ValuetoBuyers

CosttoSellers