宏观经济学课件Cha

4-1,4-2,4,GrowthandPolicy,ItemItemItemEtc.,4-3,Introduction,Chapter3explainedhowGDPandGDPgrowtharedeterminedbythesavingsrate,rateofpopulationgrowth,andtherateoftechnologicalprogressThequestionanalyzedinthischapteris“Howdosocietyschoicesaffecttheseparameters?”Inmanydevelopedcountries,inventionandadvancesintechnologyarethekeydeterminantsofgrowthTechnologicaladvancesaremuchlessimportantforpoorcountriesmoreimportanttoinvestinhumanandphysicalcapitalandborrowtechnologicaladvancesfromothersEndogenousgrowththeory(Romer,Lucas)explainshowsocietyschoicesleadtotechnologicalprogressandgrowth,4-4,TroubleWithNeoclassicalGrowthTheory,Bythelate1980stherewasgreatdissatisfactionwithneoclassicalgrowththeorysince:ItdoesnotexplaintheeconomicdeterminantsoftechnologicalprogressItpredictsthateconomicgrowthandsavingsratesareuncorrelatedinthesteadystateEndogenousgrowththeoryemphasizesdifferentgrowthopportunitiesinphysicalandknowledgecapitalDiminishingmarginalreturnstophysicalcapital,butperhapsnotknowledgecapitalTheideathatincreasedinvestmentinhumancapitalincreasesgrowthiskeytolinkinghighersavingsratestohigherequilibriumgrowthrates,4-5,MechanicsofEndogenousGrowth,Needtomodifytheproductionfunctiontoallowforself-sustaining,endogenousgrowthFigure4-1(a)showstheSolowgrowthdiagram,withthesteadystateatpointCwheresavingsequalsrequiredinvestmentIfsavingsaboverequiredinvestment,economyisgrowingasmorecapitalisaddedprocesscontinuesuntilsavingsequalsrequiredinvestment(reachthesteadystate),InsertFigure4-1(a)and(b)here,4-6,MechanicsofEndogenousGrowth,Needtomodifytheproductionfunctiontoallowforself-sustaining,endogenousgrowthFigure4-1(a)showstheSolowgrowthdiagram,withthesteadystateatpointCwheresavingsequalsrequiredinvestmentDuetothediminishingMPK,theproductionfunctionandsavingsfunctionflattenoutandcrosstheupwardslopingrequiredinvestmentlineonce,InsertFigure4-1(a)and(b)here,again,4-7,MechanicsofEndogenousGrowth,Needtomodifytheproductionfunctiontoallowforself-sustaining,endogenousgrowthEconomyillustratedinFigure4-1(b)isdescribedbyaproductionfunctionwithaconstantMPK:Y=aK(1)Kistheonlyfactor,aistheMPKProductionfunctionandsavingscurvebecomestraightlines,andarealwaysgreaterthanrequiredinvestmentthehigherthesavingsrate,thebiggerthegapbetweensavingsandrequiredinvestment=fasterthegrowth,InsertFigure4-1(a)and(b)here,again,4-8,MechanicsofEndogenousGrowth,Ifthesavingsrate,s,isconstantandthereisneitherpopulationgrowthnordepreciationofcapital,thenthechangeinthecapitalstockisdefinedas:(2)GrowthrateofcapitalisproportionaltothesavingsrateOutputisproportionaltocapital,thusthegrowthrateofoutputis(3)Thehighers,thehigherthegrowthrateofoutput,4-9,DeeperEconomicsofEndogenousGrowth,EliminatingdiminishingmarginalreturnstocapitalrunsagainstprevailingmicroeconomicprinciplesIfthereareconstantreturnstocapitalalone,therewillbeincreasingreturnstoscaletoallfactorstakentogetherlargerandlargerfirmsbecomeincreasinglyefficient,andshouldseeasinglefirmdominatetheentireeconomyNotrealistic,soneedtoeliminatethepossibilityofincreasingreturnstoscaletoallfactors,andconstantreturnstoasinglefactorAlternatively,asinglefirmmaynotcaptureallbenefitsofcapitalsomeexternaltothefirm(Romer)WhenafirmincreasesK,firmsproductionincreases,butsodoestheproductivityofotherfirmsAslongasprivatereturnhasconstantreturnstoallfactors,therewillbenotendencytowardsmonopolization,4-10,Privatevs.SocialReturnstoCapital,Investmentproducesnotonlynewmachines,butalsonewwaysofdoingthingsFirmsDOcapturetheproductionbenefitsofanewmachine(PRIVATERETURNS)FirmsmayNOTcapturethebenefitsofnewtechnologiesandideas,sincetheyareeasytocopy(SOCIALRETURNS)EndogenousgrowththeoryhingesonthenotionthattherearesubstantialexternalreturnstocapitalNotrealisticforphysicalcapital,butquiteforhumancapital:ContributionofnewknowledgeonlypartiallycapturedbycreatorFromonenewideaspringsanotherknowledgecangrowindefinitely,4-11,NandtheEndogenousGrowthModel,Assume:Technologyisproportionaltothelevelofcapitalperworker,orTechnologyislaboraugmenting,Technologygrowthdependsoncapitalgrowth,or,TheGDPgrowthequationfromChapter3wasIf,then,Derivingthegrowthequationsrequiressomealgebra.,Outputandcapitalgrowatthesamerate.,4-12,NandtheEndogenousGrowthModel,Assume:Technologyisproportionaltothelevelofcapitalperworker,orTechnologyislaboraugmenting,Technologygrowthdependsoncapitalgrowth,or,Sincethenumeratoranddenominatorofy/kgrowatequalrates,y/kisconstantWhatisthatconstant?FindbydividingtheproductionfunctionbyKandsimplifying:,Derivingthegrowthequationsrequiressomealgebra.,4-13,NandtheEndogenousGrowthModel,Assume:Technologyisproportionaltothelevelofcapitalperworker,orTechnologyislaboraugmenting,Technologygrowthdependsoncapitalgrowth,or,Theequationforcapitalaccumulationcanbewrittenas:Makingthesubstitutionfory/k,thegrowthrateofyandkbecomes:,Derivingthegrowthequationsrequiressomealgebra.,Highratesofpopulationgrowthanddepreciationleadtoalowgrowthrate.,4-14,Convergence,Doeconomieswithdifferentinitiallevelsofoutputeventuallygrowtoequalstandardsoflivingorconverge?NeoclassicalgrowththeorypredictsabsoluteconvergenceforeconomieswithequalratesofsavingandpopulationgrowthandwithaccesstothesametechnologyshouldallreachthesamesteadystatelevelofincomeConditionalconvergenceispredictedforeconomieswithdifferentratesofsavingsand/orpopulationgrowthsteadystatelevelofincomewilldiffer,butthegrowthrateswilleventuallyconvergeEndogenousgrowththeorypredictsthatahighsavingsrateleadstoahighgrowthrate,4-15,Convergence,Doeconomieswithdifferentinitiallevelsofoutputeventuallygrowtoequalstandardsoflivingorconverge?RobertBarrotestedthesecompetingtheories,andfoundthat:CountrieswithhigherlevelsofinvestmenttendtogrowfasterTheimpactofhigherinvestmentongrowthishowevertransitoryCountrieswithhigherinvestmentwillendinasteadystatewithhigherpercapitaincome,butnotwithahighergrowthrateCountriesdoappeartoconvergeconditionally,andthusendogenousgrowththeoryisnotveryusefulforexplaininginternationaldifferencesingrowthrates,4-16,GrowthTrapsandTwoSectorModels,HowdoweexplainaworldwithBOTHnogrowthANDhighgrowthcountries?Ghanaisanexampleofaneconomythathasexperiencednogrowthsince1900ChinaisanexampleofaneconomythathasexperiencedrapidgrowthinrecentyearsNeedamodelinwhichthereisapossibilityofbothanogrowth,lowincomeequilibriumANDahighgrowth,highincomeequilibriumelementsofbothneoclassicalandendogenousgrowththeories,4-17,GrowthTrapsandTwo-SectorModels,Supposetherearetwotypesofinvestmentopportunities:ThosewithdiminishingMPKatlowincomelevelsThosewithwithconstantMPKathighincomelevelsFigure4-2illustratessuchasituationTheproductionfunctionhasacurvedsegmentatlowlevelsofincomeandanupwardslopinglineathighlevelsPointAisaneoclassicalsteadystateequilibrium,whilepastpointBthereisongoinggrowth(endogenousgrowththeory),InsertFigure4-2here,4-18,GrowthTrapsandTwo-SectorModels,Supposetherearetwotypesofinvestmentopportunities:ThosewithdiminishingMPKatlowincomelevelsThosewithwithconstantMPKathighincomelevelsWithtwooutletsforinvestment,societymustchoosenotonlytotalinvestment,butalsothedivisionbetweenthetwoSocietiesthatdirectItowardsresearchanddevelopmentwillhaveongoinggrowthSocietiesthatdirectItowardphysicalcapitalmayhavehigheroutputintheshortrunattheexpenseoflowerlongrungrowth,InsertFigure4-2here,4-19,SolowModelwithEndogenousPopulationGrowth,OneoftheoldestideasineconomicsisthatpopulationgrowthworksagainsttheachievementofhighincomeTheSolowgrowthmodelpredictsthathighpopulationgrowth,n,meanslowersteadystateincomeaseachworkerwillhavelesscapitaltoworkwithOverawiderangeofincomes,populationgrowthitselfdependsonincome,n(y)Verypoorcountrieshavehighbirthratesandhighdeathrates,resultinginmoderatelyhighpopulationgrowthAsincomerises,deathratesfallandpopulationgrowthincreasesAtveryhighincomes,birthratesfall,someevenapproachingzeropopulationgrowth(ZPG),4-20,SolowModelwithEndogenousPopulationGrowth,Figure4-3illustratesthemodifiedinvestmentrequirementlineontheSolowdiagramtoaccountfornasafunctionofyTheinvestmentrequirementline,n(y)+dk,risesslowlyatlowlevelsofincome,thensharplyathigherlevels,andfinallylevelsoffathighlevelsofincome,InsertFigure4-3here,4-21,SolowModelwithEndogenousPopulationGrowth,TheinvestmentrequirementlinecrossesthesavingscurveatpointsA,B,andCPointAisapovertytrapwithhighpopulationgrowthandlowincomesPointChaslowpopulationgrowthathighincomesPointsAandCarestableequilibriumsbecausetheeconomymovestowardsthesepointsPointBisanunstableequilibriumsincetheeconomymovesawayfromit,InsertFigure4-3hereagain,4-22,SolowModelwithEndogenousPopulationGrowth,Howcananeconomyescapefromthelow-lev