宏观经济学ppt课件 (10).ppt

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1、®CHAPTER16ConsumptionMANKIW'SMACROECONOMICSMODULES1JohnMaynardKeynesandtheConsumptionFunctionTheconsumptionfunctionwascentraltoKeynes’theoryofeconomicfluctuationspresentedinTheGeneralTheoryin1936.Keynesconjecturedthatthemarginalpropensitytoconsume—theamountconsumedoutofanaddit

2、ionaldollarofincomeisbetweenzeroandone.Heclaimedthatthefundamentallawisthatoutofeverydollarofearnedincome,peoplewillconsumepartofitandsavetherest.Keynesalsoproposedtheaveragepropensitytoconsume,theratioofconsumptiontoincomefallsasincomerises.Keynesalsoheldthatincomeistheprimar

3、ydeterminantofconsumptionandthattheinterestratedoesnothaveanimportantrole.2TheConsumptionFunctionConsumptionspendingbyhouseholdsdependsonautonomousconsumptionmarginalpropensitytoconsume(MPC)disposableincomeC=C+cY,C>0,0

4、heconsumptionfunctionislowercasec,theMPC.C=C+cY3TheAveragePropensitytoConsumeCYCAPC=C/Y=C/Y+c11APC1APC2ThisconsumptionfunctionexhibitsthreepropertiesthatKeynesconjectured.First,themarginalpropensitytoconsumecisbetweenzeroandone.Second,theaveragepropensitytoconsumefallsasincome

5、rises.Third,consumptionisdeterminedbycurrentincomeY.AsYrises,C/Yfalls,andsotheaveragepropensitytoconsumeC/Yfalls.Noticethattheinterestrateisnotincludedinthisequationasadeterminantofconsumption.4TheMarginalPropensitytoConsumeTounderstandthemarginalpropensitytoconsume(MPC),consi

6、derashoppingscenario.ApersonwholovestoshopprobablyhasalargeMPC,let’ssay(.99).Thismeansthatforeveryextradollarheorsheearnsaftertaxdeductions,heorshespends$.99ofit.TheMPCmeasuresthesensitivityofthechangeinonevariable,consumption,withrespecttoachangeintheothervariable,income.5Sec

7、ularStagnation,SimonKuznets,andtheConsumptionPuzzleDuringWorldWarII,onthebasisofKeynes’sconsumptionfunction,economistspredictedthattheeconomywouldexperiencewhattheycalledsecularstagnation—alongdepressionofinfiniteduration—unlessthegovernmentusedfiscalpolicytostimulateaggregate

8、demand.ItturnedoutthattheendofthewardidnotthrowtheUnitedState