多恩布什宏观经济学第十版课后习题答案08.doc
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多恩布什宏观经济学第十版课后习题答案08.doc
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·CHAPTER8
SolutionstotheProblemsintheTextbook:
ConceptualProblems:
1. Thefirstquestionyoushouldaskyourselfasapolicymakeriswhetheradisturbanceistransitoryorpersistent.Youshouldthenaskyourselfhowlongitwouldtaketoputasuggestedpolicymeasureintoeffectandhowlongitwilltakeforthepolicytohavethedesiredeffectontheeconomy.Inaddition,youneedtoknowhowreliabletheestimatesofyouradvisorsareabouttheeffectsofthepolicy.Ifadisturbanceissmallandprobablytransitory,youmaybebestadvisedtodonothing,becauseanymeasureyoutakeislikelytohaveitseffectaftertheeconomyhasrecovered.Thereforeyouractionmightonlyfurtheraggravatetheproblem.
2.a. Theinsidelagisthetimeittakesafteraneconomicdisturbancehasoccurredtorecognizeandimplementapolicyactionthatwilladdressthedisturbance.
2.b. Theinsidelagisdividedintothreeparts.First,thereistherecognitionlag,thatis,thetimeittakesforpolicymakerstorealizethatadisturbancehasoccurredandthatapolicyresponseiswarranted.Second,thereisthedecisionlag,thatis,thetimeittakestodecideonthemostdesirablepolicyresponseafteradisturbanceisrecognized.Finally,thereistheactionlag,thatis,thetimeittakestoactuallyimplementthepolicymeasure.
2.c. InsidelagsareshorterformonetarypolicythanforfiscalpolicysincetheFOMCmeetsonaregularbasistodiscussandimplementmonetarypolicy.Fiscalpolicy,ontheotherhand,hastobeinitiatedandpassedbybothhousesoftheU.S.Congressandthiscanbealengthyprocess.Theexceptionsaretheso-calledautomaticstabilizers;however,theyonlyworkwellforsmallandtransitorydisturbances
2.d Automaticstabilizershavenoinsidelag;theyareendogenousandfunctionwithoutspecificgovernmentintervention.Examplesaretheincometaxsystem,thewelfaresystem,unemploymentinsurance,andtheSocialSecuritysystem.Theyallreducetheamountbywhichoutputchangesinresponsetoaneconomicdisturbance.
3.a. Theoutsidelagisthetimeittakesforapolicyaction,onceimplemented,tohaveitsfulleffectontheeconomy.
3.b. Generally,theoutsidelagisadistributedlagwithasmallimmediateeffectandalargeroveralleffectoveralongertimeperiod.Theeffectisspreadovertime,sinceaggregatedemandrespondstoanypolicychangeonlyslowlyandwithalag.
3.c. Outsidelagsarelongerformonetarypolicysincemonetarypolicyactionsaffectshort-terminterestratesmostdirectly,whileaggregatedemanddependsheavilyonlaggedvaluesofincome,interestrates,andothereconomicvariables.Achangeingovernmentspending,however,immediatelyaffectsaggregatedemand.
4. Fiscalpolicyhassmalleroutsidelags,butsignificantinsidelags.Monetarypolicy,ontheotherhandhassmallerinsidelagsandlongeroutsidelags.Thereforelargeopenmarketoperationsshouldbeundertakentogetanimmediateeffect,buttheyshouldbepartiallyreversedovertimetoavoidalargelong-runeffect.Iftheshockissufficientlytransitoryandsmall,policymakersmaybebestadvisednottoundertakeanypolicychangeatall.
5.a. Aneconometricmodelisastatisticaldescriptionofallorpartoftheeconomy.Itconsistsofasetofequationsthatarebasedonpasteconomicbehavior.
5.b. Econometricmodelsaregenerallyusedtoforecastthebehavioroftheeconomyandtheeffectsofalternativepolicymeasures.
5.c. Thereisconsiderableuncertaintyabouthowwelleconometricmodelsactuallyrepresenttheworkingsoftheeconomy.Thereisalsogreatuncertaintyabouttheexpectationsoffirmsandconsumersandtheirreactionstopolicychanges.Anypolicyisboundtofailiftheinformationonwhichitwasbasedispoor.
6.Theanswertothisquestionisstudentspecific.Themaindifficultiesofstabilizationpolicyarisefromthreesources.First,policyalwaysworkswithlags.Second,theoutcomeofanypolicydependsonthewaytheprivatesectorformsexpectationsandhowthoseexpectationsaffectthepublic'sbehavior.Third,thereisconsiderableuncertaintyaboutthestructureoftheeconomyandtheshocksthathitit.
ItcanbearguedthatamonetarypolicyrulewouldgreatlyreduceuncertaintyabouttheFed'spolicyresponses.Ifthegovernmentbehavedinaconsistentway,thentheprivatesectorwouldalsobehavemoreconsistentlyandeconomicfluctuationscouldbegreatlyreduced.AmonetarygrowthrulewouldalsoreduceanypoliticalpressuretheadministrationmightexertontheFed.Itisofteninitiallyunclearwhetheradisturbanceistemporaryorpersistentandamonetarypolicyrulewouldpreventpolicymistakesincaseswherethedisturbanceis,infact,temporary.Ifactivemonetarypolicyisappliedtoatemporarydisturbance,thenthelagsinvolvedwillguaranteethattheeconomywillactuallybedestabilized.
Ontheotherhand,theworkingsoftheeconomyarenotcompletelyunderstoodandeventscannotalwaysbepredicted.Thusitisdifficulttoargueforafixedpolicyrule.Unanticipatedlargedisturbanceswarrantanactivistpolicy,especiallyiftheyappeartobepersistent.Itisalsopossibletoconstructamoreactivistmonetarygrowthrule.Forexample,Equation(8)suggeststhattheannualmonetarygrowthrateshouldbeincreasedbytwopercentforeveryonepercentthatunemploymentincreasesaboveitsnaturalrate.Sucharuleisbasedonthequantitytheoryofmoneyequation(whichrelatesmoneysupplygrowthtothegrowthofnominalGDP)andonOkun'slaw(whichrelatestheunemploymentratetoeconomicgrowth).Obviously,becauseofthelonglagsformonetarypolicy,anymonetarygrowthrulewillworkmuchbetterinthelongrunthanintheshortrun.
Fiscalpolicyrulesmaymakemoresensethanmonetarypolicyrules,sincefiscalpolicyhaslonginsidelagsbutshorteroutsidelags.Inaway,built-instabilizers,althoughgenerallynotconsidered"rules",alreadyprovidesomestabilitywithoutanyinsidelag.Manyoftheargumentsagainstmonetarypolicyrulesarealsovalidforfiscalpolicyrulesandmanyeconomistsopposethem.Thefrequentlyproposedconstitutionalamendmentrequiringanannuallybalancedbudgetisanexampleofafiscalpolicyrule.Therearesignificantproblemsassociatedwithsuchanamendment,sinceitwouldgreatlylimitthegovernment'sabilitytoundertakeactivefiscalstabilizationpolicy.
7. Theargumentsforaconstantgrowthrateruleformoneyarebasedonthequantitytheoryofmoneyequation,thatis,
MV=PY.
Fromthisequationwecanderive
%DP=%DM-%DY+%DV.
Ifthelong-runtrendrateofrealoutput(Y)andthelong-runtrendofvelocity(V)areassumedtobefairlystable,andifwagesandpricesaresufficientlyflexible,thenaconstantmonetarygrowthrate(M)wouldinsureaconstantrateofinflation,thatis,aconstantrateofchangeinthepricelevel(P).Also,sincemonetarypolicyhaslongoutsidelags,activemonetarypolicycanactuallybemoredestabilizingthanstabilizing.Inaddition,sincewedonotknowexactlyhowtheeconomyworksormayreacttospecificpolicies,itisbesttofollowaruleratherthanundertakeactionsthathaveuncertainoutcomes.However,rulesarenotwithoutproblems,astheywouldnotallowflexibilityinrespondingtomajordisturbances.
8. Dynamicinconsistencyoccursif,afterhavingcommittedthemselvestoaspecificpolicyactiondesignedtoachievealong-runobjective,policymakersfindthemselvesinasituationwhereitseemsadvantageoustoabandontheiroriginalpolicy,inordertoachieveashort-rungoal.Suchactionwillimpedethelong-runobjective.
9. RealGDPtargetingisthebestoptioniftheprimarypolicygoalofmonetarypolicyistoachievefullemployment.IfpolicymakersforecastpotentialGDPcorrectly,thenfullemploymentcombinedwithlowinflationcanbeachieved.However,realGDPtargetingbearsthegreaterriskthatthesecondarygoalofachievingalowinflationratewillbemissed.IftherateatwhichpotentialGDPgrowsisoverestimated,thenpolicymakersmaystimulatetheeconomytoomuch.Inthiscase,theywillnotbesuccessfulinachievingpricestability.BytargetingnominalGDP,thecentralbankcreatesapolicytradeoffbetweeninflationandunemployment.IftherateatwhichpotentialGDPgrowsisoverestimatedandpolicymakersstimulatetheeconomytoomuch,wewillgetlessgrowthbutalsolessinflationthanunderrealGDPtargeting.WhichtargetingapproachshouldbechosendependsgreatlyonhowsteeporflatthePhillipscurveisperceivedtobe.
TechnicalProblems:
1. IfactualGDPisexpectedtobe$40billionbelowthefull-employmentlevelandthesizeofthegovernmentspendingmultiplieris2,thengovernmentspendingshouldbeincreasedby$20billionoveritscurrentlevel.Forthenextperiod,whenactualGDPisexpectedtobe$20billionbelowpotential,governmentspendingshouldbecutby$10billionfromitsnewlevel,thatis,to$10billionoveritsoriginallevel.Inperiodthree,whenactualGDPisexpectedtobeatitsfull-employmentlevel,thelevelofgovernmentspendingshouldagainbecutby$10billionfromthelastperiod'sleveltobringitbacktotheoriginallevelofPeriod0.
2.a. Ifthereisaone-periodoutsidelagforgovernmentspending,thennothingcanbedonetoclosethecurrentGDP-gap.Thegovernmentshoulddecidetospend$10billionmoreforthenextperiodandreducespendingagaintoitsoriginallevelafterthat.
2.b. GraphIbelowshowsthepathofGDPforProblem1withnooutsidelagandGraphIIshowsthepathofGDPforproblem2.a.withaone-periodoutsidelag.Ineachofthegraphsthep
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