多恩布什宏观经济学第十版课后习题答案09Word文档下载推荐.doc
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多恩布什宏观经济学第十版课后习题答案09Word文档下载推荐.doc
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1.a.AD=C+I=100+(0.8)Y+50=150+(0.8)Y
TheequilibriumconditionisY=AD==>
Y=150+(0.8)Y==>
(0.2)Y=150==>
Y=5*150=750.
1.b.SinceTA=TR=0,itfollowsthatS=YD-C=Y-C.Therefore
S=Y-[100+(0.8)Y]=-100+(0.2)Y==>
S=-100+(0.2)750=-100+150=50.
1.c.IfthelevelofoutputisY=800,thenAD=150+(0.8)800=150+640=790.
ThereforetheamountofinvoluntaryinventoryaccumulationisUI=Y-AD=800-790=10.
1.d.AD'
=C+I'
=100+(0.8)Y+100=200+(0.8)Y
FromY=AD'
==>
Y=200+(0.8)Y==>
(0.2)Y=200==>
Y=5*200=1,000
Note:
Thisresultcanalsobeachievedbyusingthemultiplierformula:
DY=(multiplier)(DSp)=(multiplier)(DI)==>
DY=5*50=250,
thatis,outputincreasesfromYo=750toY1=1,000.
1.e.From1.a.and1.d.wecanseethatthemultiplieris5.
1.f. Sp Y=Sp
AD1=200=(0.8)Y
ADo=150+(0.8)Y
200
150
0
7501,000 Y
2.a.Sincethempchasincreasedfrom0.8to0.9,thesizeofthemultiplierisnowlargerandweshouldthereforeexpectahigherequilibriumincomelevelthanin1.a.
AD=C+I=100+(0.9)Y+50=150+(0.9)Y==>
Y=AD==>
Y=150+(0.9)Y==>
(0.1)Y=150==>
Y=10*150=1,500.
2.b.FromDY=(multiplier)(DI)=10*50=500==>
Y1=Yo+DY=1,500+500=2,000.
2.c.Sincethesizeofthemultiplierhasdoubledfrom5to10,thechangeinoutput(Y)thatresultsfromachangeininvestment(I)nowhasalsodoubledfrom250to500.
2.d.Sp Y=Sp
AD1=200=(0.9)Y
ADo=150+(0.9)Y
0 1,5002,000 Y
3.a.AD=C+I+G+NX=50+(0.8)YD+70+200=320+(0.8)[Y-(0.2)Y+100]
=400+(0.8)(0.8)Y=400+(0.64)Y
FromY=AD==>
Y=400+(0.64)Y==>
(0.36)Y=400
==>
Y=(1/0.36)400=(2.78)400=1,111.11
Thesizeofthemultiplieris(1/0.36)=2.78.
3.b.BS=tY-TR-G=(0.2)(1,111.11)-100-200=222.22-300=-77.78
3.c.AD'
=320+(0.8)[Y-(0.25)Y+100]=400+(0.8)(0.75)Y=400+(0.6)Y
FromY=AD'
==>
Y=400+(0.6)Y==>
(0.4)Y=400==>
Y=(2.5)400=1,000
Thesizeofthemultiplierisnowreducedto2.5.
3.d.BS'
=(0.25)(1,000)-100-200=-50
BS'
-BS=-50-(-77.78)=+27.78
Thesizeofthemultiplierandequilibriumoutputwillbothincreasewithanincreaseinthemarginalpropensitytoconsume.Thereforeincometaxrevenuewillalsogoupandthebudgetsurplusshouldincrease.
3.e.Iftheincometaxrateist=1,thenallincomeistaxed.Thereisnoinducedspendingandequilibriumincomeonlyincreasesbythechangeinautonomousspending,thatis,thesizeofthemultiplieris1.
FromY=C+I+G==>
Y=Co+c(Y-1Y+TRo)+Io+Go
==>
Y=Co+cTRo+Io+Go=Ao
4.InProblem3.d.wehadasituationwherethefollowingwasgiven:
Y=1,000,t=0.25,G=200andBS=-50.
Assumenowthatt=0.3andG=250==>
AD'
=50+(0.8)[Y-(0.3)Y+100]+70+250=370+(0.8)(0.7)Y+80=450+(0.56)Y.
FromY=AD'
Y=450+(0.56)Y==>
(0.44)Y=450
==>
Y=(1/0.44)450=1,022.73
BS'
=(0.3)(1,022.73)-100-250=306.82-350=-43.18
-BS=-43.18-(-50)=+6.82
Thebudgetsurplushasincreased,sincetheincreaseintaxrevenueislargerthantheincreaseingovernmentpurchases.
5.a.WhileanincreaseingovernmentpurchasesbyDG=10willchangeintendedspendingbyDSp=10,adecreaseingovernmenttransfersbyDTR=-10willchangeintendedspendingbyasmalleramount,thatis,byonlyDSp=c(DTR)=c(-10).ThechangeinintendedspendingequalsDSp=(1-c)(10)andequilibriumincomeshouldthereforeincreaseby
DY=(multiplier)(1-c)10.
5.b.Ifc=0.8andt=0.25,thenthesizeofthemultiplieris
a=1/[1-c(1-t)]=1/[1-(0.8)(1-0.25)]=1/[1-(0.6)]=1/(0.4)=2.5.
Thechangeinequilibriumincomeis
DY=a(DAo)=a[DG+c(DTR)]=(2.5)[10+(0.8)(-10)]=(2.5)2=5
5.c.DBS=t(DY)-DTR-DG=(0.25)(5)-(-10)-10=1.25
AdditionalProblems:
1."
Anincreaseinthemarginalpropensitytosaveincreasestheimpactofoneadditionaldollarinincomeonconsumption."
Commentonthisstatement.Inyouranswerdiscusstheeffectofsuchachangeinthempsonthesizeoftheexpendituremultiplier.
Thefactthatthemarginalpropensitytosave(1-c)hasrisenimpliesthatthemarginalpropensitytoconsume(c)hasfallen.Thismeansthatnowoneextradollarinincomeearnedwillaffectconsumptionbylessthanbeforethereductioninthempc.Whenthempcishigh,oneextradollarinincomeraisesconsumptionbymorethanwhenthempcislow.Ifthempsislarger,thentheexpendituremultiplierwillbelarger,sincetheexpendituremultiplierisdefinedas1/(1-c).
2.Usingasimplemodeloftheexpendituresectorwithoutanygovernmentinvolvement,explaintheparadoxofthriftthatassertsthatadesiretosavemaynotleadtoanincreaseinactualsaving.
Theparadoxofthriftoccursbecausethedesiretoincreasesavingleadstoalowerconsumptionlevel.Butalowerlevelofspendingsendstheeconomyintoarecessionandwegetanewequilibriumatalowerlevelofoutput.Intheend,theincreaseinautonomoussavingisexactlyoffsetbythedecreaseininducedsavingduetothelowerincomelevel.Inotherwords,theeconomyisinequilibriumwhenS=Io.Sincethelevelofautonomousinvestment(Io)hasnotchanged,thelevelofsavingatthenewequilibriumincomelevelmustalsoequalIo.
Thiscanalsobederivedmathematically.Sinceanincreaseindesiredsavingisequivalenttoadecreaseindesiredconsumption,thatis,DCo=-DSo,theeffectonequilibriumincomeis
DY=[1/(1-c)](DCo)=[1/(1-c)](-DSo).
Thereforetheoveralleffectontotalsavingis
DS=s(DY)+DSo=[s/(1-c)](-DSo)+DSo=0,sinces=1-c.
3. "
Whenaggregatedemandfallsbelowthecurrentoutputlevel,anunintendedinventoryaccumula
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