微观经济学课件清华大学 Tsinghua Micro Ch10 021011.ppt

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1、ChapterTenIntertemporalChoiceWhatAreWeDoinginthisChapter?Weapplyourbasicframeworkofconsumerchoicetostudyissuesofchoicesacrossdifferenttimeperiods;Again,intermsoftheoreticalframework,notmuchisnew!WhatAretheQuestions?Personsoftenreceiveincomein“lumps”;e.g.monthlysalary.Howisalumpof

2、incomespreadoverthefollowingmonth(savingnowforconsumptionlater)?Orhowisconsumptionfinancedbyborrowingnowagainstincometobereceivedattheendofthemonth?PresentandFutureValuesBeginwithsomesimplefinancialarithmetic.Takejusttwoperiods;1and2.Letrdenotetheinterestrateperperiod.FutureValue

3、Givenaninterestraterthefuturevalueoneperiodfromnowof$misPresentValueQ:Howmuchmoneywouldhavetobesavednow,inthepresent,toobtain$1atthestartofthenextperiod?A:$msavednowbecomes$m(1+r)atthestartofnextperiod,sowewantthevalueofmforwhichm(1+r)=1Thatis,m=1/(1+r),thepresent-valueof$1obt

4、ainedatthestartofnextperiod.PresentValueThepresentvalueof$1availableatthestartofthenextperiodisAndthepresentvalueof$mavailableatthestartofthenextperiodisTheIntertemporalChoiceProblemLetm1andm2beincomesreceivedinperiods1and2.Letc1andc2beconsumptionsinperiods1and2.Letp1andp2bethepr

5、icesofconsumptioninperiods1and2.TheIntertemporalChoiceProblemTheintertemporalchoiceproblem:Givenincomesm1andm2,andgivenconsumptionpricesp1andp2,whatisthemostpreferredintertemporalconsumptionbundle(c1,c2)?Forananswerweneedtoknow:theintertemporalbudgetconstraintintertemporalconsump

6、tionpreferences.TheIntertemporalBudgetConstraintTostart,let’signorepriceeffectsbysupposingthatp1=p2=$1.TheIntertemporalBudgetConstraintc1c2So(c1,c2)=(m1,m2)istheconsumptionbundleiftheconsumerchoosesneithertosavenortoborrow.m2m100TheIntertemporalBudgetConstraintc1c2m2m100thef

7、uture-valueoftheincomeendowmentTheIntertemporalBudgetConstraintc1c2m2m100istheconsumptionbundlewhenallperiod1incomeissaved.TheIntertemporalBudgetConstraintNowsupposethattheconsumerspendseverythingpossibleonconsumptioninperiod1,soc2=0.Whatisthemostthattheconsumercanborrowinperio

8、d1againstherperiod2incomeof$m2?Letb1deno