Lecture 9 - Neoclassical Endogenous Growth

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1、14.452EconomicGrowth:Lecture9,NeoclassicalEndogenousGrowthDaronAcemogluMITNovember29,2011.DaronAcemoglu(MIT)EconomicGrowthLecture9November29,2011.1/41First-GenerationModelsofEndogenousGrowthModelssofar:nosustainedlong-rungrowth;relativelylittletosayaboutsources

2、oftechnologydi¤erences.Modelsinwhichtechnologyevolvesasaresultof…rms’andworkers’decisionsaremostattractiveinthisregard.Butsustainedeconomicgrowthispossibleintheneoclassicalmodelaswell:AKmodelbefore:relaxedAssumption2andpreventeddiminishingreturnstocapital.Capit

3、alaccumulationcouldactastheengineofsustainedeconomicgrowth.NeoclassicalversionoftheAKmodel:Verytractableandapplicationsinmanyareas.Shortcoming:capitalisessentiallytheonlyfactorofproduction,asymptoticallyshareofincomeaccruingtoittendsto1.Two-sectorendogenousgrow

4、thmodelsbehaveverysimilarlytothebaselineAKmodel,butavoidthis.DaronAcemoglu(MIT)EconomicGrowthLecture9November29,2011.2/41Demographics,PreferencesandTechnologyIFocusonbalancedeconomicgrowth,i.e.consistentwiththeKaldorfacts.ThusCRRApreferencesasinthecanonicalneoc

5、lassicalgrowthmodel.Economyadmitsanin…nitely-livedrepresentativehousehold,householdsizegrowingattheexponentialraten.Preferences"#Z∞1θc(t)1U=exp((ρn)t)dt.(1)01θLaborissuppliedinelastically.Flowbudgetconstraint,a˙(t)=(r(t)n)a(t)+w(t)c(t),(2)DaronAcemoglu(M

6、IT)EconomicGrowthLecture9November29,2011.3/41Demographics,PreferencesandTechnologyIINo-Ponzigameconstraint:Ztlima(t)exp[r(s)n]ds0.(3)t!∞0Eulerequation:c˙(t)1=(r(t)ρ).(4)c(t)θTransversalitycondition,Ztlima(t)exp[r(s)n]ds=0.(5)t!∞0Problemisconcave,s

7、olutiontothesenecessaryconditionsisinfactanoptimalplan.Finalgoodsectorsimilartobefore,butAssumptions1and2arenotsatis…ed.DaronAcemoglu(MIT)EconomicGrowthLecture9November29,2011.4/41Demographics,PreferencesandTechnologyIIIMorespeci…cally,Y(t)=AK(t),withA>0.Doesno

8、tdependonlabor,thusw(t)in(2)willbeequaltozero.De…ningk(t)K(t)/L(t)asthecapital-laborratio,Y(t)y(t)L(t)=Ak(t).(6)Noticeoutputisonlyafunctionofcapital,andtherearenodiminishi