曼昆 宏观经济经济学第九版 英文原版答案3.docx

曼昆 宏观经济经济学第九版 英文原版答案3.docx

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曼昆宏观经济经济学第九版英文原版答案3

AnswerstoTextbookQuestionsandProblems

CHAPTER3 NationalIncome:

WhereItComesFromandWhereItGoes

QuestionsforReview

1.Thefactorsofproductionandtheproductiontechnologydeterminetheamountofoutputaneconomycanproduce.Thefactorsofproductionaretheinputsusedtoproducegoodsandservices:

themostimportantfactorsarecapitalandlabor.Theproductiontechnologydetermineshowmuchoutputcanbeproducedfromanygivenamountsoftheseinputs.Anincreaseinoneofthefactorsofproductionoranimprovementintechnologyleadstoanincreaseintheeconomy’soutput.

2.Whenafirmdecideshowmuchofafactorofproductiontohireordemand,itconsidershowthisdecisionaffectsprofits.Forexample,hiringanextraunitoflaborincreasesoutputandthereforeincreasesrevenue;thefirmcomparesthisadditionalrevenuetotheadditionalcostfromthehigherwagebill.Theadditionalrevenuethefirmreceivesdependsonthemarginalproductoflabor（MPL）andthepriceofthegoodproduced（P）.AnadditionalunitoflaborproducesMPLunitsofadditionaloutput,whichsellsforPdollarsperunit.Therefore,theadditionalrevenuetothefirmisPMPL.ThecostofhiringtheadditionalunitoflaboristhewageW.Thus,thishiringdecisionhasthefollowingeffectonprofits:

ΔProfit=ΔRevenue–ΔCost

=（PMPL）–W.

Iftheadditionalrevenue,PMPL,exceedsthecost（W）ofhiringtheadditionalunitoflabor,thenprofitincreases.Thefirmwillhirelaboruntilitisnolongerprofitabletodoso—thatis,untiltheMPLfallstothepointwherethechangeinprofitiszero.Intheequationabove,thefirmhireslaboruntilΔProfit=0,whichiswhen（PMPL）=W.

Thisconditioncanberewrittenas:

MPL=W/P.

Therefore,acompetitiveprofit-maximizingfirmhireslaboruntilthemarginalproductoflaborequalstherealwage.Thesamelogicappliestothefirm’sdecisionregardinghowmuchcapitaltohire:

thefirmwillhirecapitaluntilthemarginalproductofcapitalequalstherealrentalprice.

3.Aproductionfunctionhasconstantreturnstoscaleifanequalpercentageincreaseinallfactorsofproductioncausesanincreaseinoutputofthesamepercentage.Forexample,ifafirmincreasesitsuseofcapitalandlaborby50percent,andoutputincreasesby50percent,thentheproductionfunctionhasconstantreturnstoscale.

Iftheproductionfunctionhasconstantreturnstoscale,thentotalincome（orequivalently,totaloutput）inaneconomyofcompetitiveprofit-maximizingfirmsisdividedbetweenthereturntolabor,MPLL,andthereturntocapital,MPKK.Thatis,underconstantreturnstoscale,economicprofitiszero.

4.ACobb–DouglasproductionfunctionhastheformF（K,L）=AKαL1–α.Thetextshowedthattheparameterαgivescapital’sshareofincome.Soifcapitalearnsone-fourthoftotalincome,thenα=0.25.Hence,F（K,L）=AK0.25L0.75.

5.Consumptiondependspositivelyondisposableincome—i.e.theamountofincomeafteralltaxeshavebeenpaid.Higherdisposableincomemeanshigherconsumption.

Thequantityofinvestmentgoodsdemandeddependsnegativelyontherealinterestrate.Foraninvestmenttobeprofitable,itsreturnmustbegreaterthanitscost.Becausetherealinterestratemeasuresthecostoffunds,ahigherrealinterestratemakesitmorecostlytoinvest,sothedemandforinvestmentgoodsfalls.

6.Governmentpurchasesareameasureofthevalueofgoodsandservicespurchaseddirectlybythegovernment.Forexample,thegovernmentbuysmissilesandtanks,buildsroads,andprovidesservicessuchasairtrafficcontrol.AlloftheseactivitiesarepartofGDP.Transferpaymentsaregovernmentpaymentstoindividualsthatarenotinexchangeforgoodsorservices.Theyaretheoppositeoftaxes:

taxesreducehouseholddisposableincome,whereastransferpaymentsincreaseit.ExamplesoftransferpaymentsincludeSocialSecuritypaymentstotheelderly,unemploymentinsurance,andveterans’benefits.

7.Consumption,investment,andgovernmentpurchasesdeterminedemandfortheeconomy’soutput,whereasthefactorsofproductionandtheproductionfunctiondeterminethesupplyofoutput.Therealinterestrateadjuststoensurethatthedemandfortheeconomy’sgoodsequalsthesupply.Attheequilibriuminterestrate,thedemandforgoodsandservicesequalsthesupply.

8.Whenthegovernmentincreasestaxes,disposableincomefalls,andthereforeconsumptionfallsaswell.Thedecreaseinconsumptionequalstheamountthattaxesincreasemultipliedbythemarginalpropensitytoconsume（MPC）.ThehighertheMPCis,thegreateristhenegativeeffectofthetaxincreaseonconsumption.Becauseoutputisfixedbythefactorsofproductionandtheproductiontechnology,andgovernmentpurchaseshavenotchanged,thedecreaseinconsumptionmustbeoffsetbya