宏观经济学---曼昆chap07.ppt

宏观经济学---曼昆chap07.ppt

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EconomicGrowthI:

CapitalAccumulationandPopulationGrowthChapter7CHAPTER7EconomicGrowthIInthischapter,youwilllearnltheclosedeconomySolowmodellhowacountrysstandardoflivingdependsonitssavingandpopulationgrowthrateslhowtousethe“GoldenRule”tofindtheoptimalsavingrateandcapitalstockCHAPTER7EconomicGrowthIWhygrowthmatterslDataoninfantmortalityrates:

m20%inthepoorest1/5ofallcountriesm0.4%intherichest1/5lInPakistan,85%ofpeopleliveonlessthan$2/day.lOne-fourthofthepoorestcountrieshavehadfaminesduringthepast3decades.lPovertyisassociatedwithoppressionofwomenandminorities.Economicgrowthraiseslivingstandardsandreducespoverty.Incomeandpovertyintheworldselectedcountries,2000CHAPTER7EconomicGrowthIWhygrowthmatterslAnythingthateffectsthelong-runrateofeconomicgrowthevenbyatinyamountwillhavehugeeffectsonlivingstandardsinthelongrun.1,081.4%243.7%85.4%624.5%169.2%64.0%2.5%2.0%100years50years25yearspercentageincreaseinstandardoflivingafterannualgrowthrateofincomepercapitaCHAPTER7EconomicGrowthIWhygrowthmatterslIftheannualgrowthrateofU.S.realGDPpercapitahadbeenjustone-tenthofonepercenthigherduringthe1990s,theU.S.wouldhavegeneratedanadditional$496billionofincomeduringthatdecade.CHAPTER7EconomicGrowthIThelessonsofgrowththeorycanmakeapositivedifferenceinthelivesofhundredsofmillionsofpeople.TheselessonshelpusmunderstandwhypoorcountriesarepoormdesignpoliciesthatcanhelpthemgrowmlearnhowourowngrowthrateisaffectedbyshocksandourgovernmentspoliciesCHAPTER7EconomicGrowthITheSolowmodellduetoRobertSolow,wonNobelPrizeforcontributionstothestudyofeconomicgrowthlamajorparadigm:

mwidelyusedinpolicymakingmbenchmarkagainstwhichmostrecentgrowththeoriesarecomparedllooksatthedeterminantsofeconomicgrowthandthestandardoflivinginthelongrunCHAPTER7EconomicGrowthIHowSolowmodelisdifferentfromChapter3smodel1.Kisnolongerfixed:

investmentcausesittogrow,depreciationcausesittoshrink2.Lisnolongerfixed:

populationgrowthcausesittogrow3.theconsumptionfunctionissimplerCHAPTER7EconomicGrowthIHowSolowmodelisdifferentfromChapter3smodel4.noGorT（onlytosimplifypresentation;wecanstilldofiscalpolicyexperiments）5.cosmeticdifferencesCHAPTER7EconomicGrowthITheproductionfunctionlInaggregateterms:

Y=F（K,L）lDefine:

y=Y/L=outputperworkerk=K/L=capitalperworkerlAssumeconstantreturnstoscale:

zY=F（zK,zL）foranyz0lPickz=1/L.ThenY/L=F（K/L,1）y=F（k,1）y=f（k）wheref（k）=F（k,1）2005PearsonEducation,Inc.CHAPTER7EconomicGrowthITheproductionfunctionOutputperworker,yCapitalperworker,kf（k）Note:

thisproductionfunctionexhibitsdiminishingMPK.1MPK=f（k+1）f（k）CHAPTER7EconomicGrowthIThenationalincomeidentitylY=C+I（remember,noG）lIn“perworker”terms:

y=c+iwherec=C/Landi=I/LCHAPTER7EconomicGrowthITheconsumptionfunctionls=thesavingrate,thefractionofincomethatissaved（sisanexogenousparameter）Note:

sistheonlylowercasevariablethatisnotequaltoitsuppercaseversiondividedbyLlConsumptionfunction:

c=（1s）y（perworker）CHAPTER7EconomicGrowthISavingandinvestmentlsaving（perworker）=yc=y（1s）y=sylNationalincomeidentityisy=c+iRearrangetoget:

i=yc=sy（investment=saving,likeinchap.3!

）lUsingtheresultsabove,i=sy=sf（k）2005PearsonEducation,Inc.CHAPTER7EconomicGrowthIOutput,consumption,andinvestmentOutputperworker,yCapitalperworker,kf（k）sf（k）k1y1i1c12005PearsonEducation,Inc.CHAPTER7EconomicGrowthIDepreciationDepreciationperworker,kCapitalperworker,kk=therateofdepreciation=thefractionofthecapitalstockthatwearsouteachperiod1CHAPTER7EconomicGrowthICapitalaccumulationChangeincapitalstock=investmentdepreciationk=ikSincei=sf（k）,thisbecomes:

k=sf（k）kThebasicidea:

Investmentincreasesthecapitalstock,depreciationreducesit.CHAPTER7EconomicGrowthITheequationofmotionforklTheSolowmodelscentralequationlDeterminesbehaviorofcapitalovertimelwhich,inturn,determinesbehaviorofalloftheotherendogenousvariablesbecausetheyalldependonk.E.g.,incomeperperson:

y=f（k）consumptionperperson:

c=（1s）f（k）k=sf（k）kCHAPTER7EconomicGrowthIThesteadystateIfinvestmentisjustenoughtocoverdepreciationsf（k）=k,thencapitalperworkerwillremainconstant:

k=0.Thisoccursatonevalueofk,denotedk*,calledthesteadystatecapitalstock.k=sf（k）k2005PearsonEducation,Inc.CHAPTER7EconomicGrowthIThesteadystateInvestmentanddepreciationCapitalperworker,ksf（k）kk*2005PearsonEducation,Inc.CHAPTER7EconomicGrowthIMovingtowardthesteadystateInvestmentanddepreciationCapitalperworker,ksf（k）kk*k=sf（k）kdepreciationkk1investment2005PearsonEducation,Inc.CHAPTER7EconomicGrowthIMovingtowardthesteadyst