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1、Long-TermPortfolioChoiceJohnY.CampbellEc2723November2011JohnY.Campbell(Ec2723)Long-TermPortfolioChoiceNovember20111/35OutlineMyopicportfoliochoice:investmentrulesthatdonotdependontheinvestmenthorizon.IEpstein-Zinutilitywitheitheriidreturnsorγ=1.Long-term
2、portfoliochoice:investmentrulesthatdodependontheinvestmenthorizon.AssumeEpstein-Zinutilityandγ6=1.ITime-varyinginterestrates(Campbell-ViceiraChapter3.)ITime-varyingriskpremia(CVChapter4.)IApplicationstothecross-sectionofstockreturns(intertemporalCAPM).IL
3、aborincome,animplicitholdingofhumancapitalwhosevaluedependsonthehorizon(CVChapters6and7.)JohnY.Campbell(Ec2723)Long-TermPortfolioChoiceNovember20112/35MyopicPortfolioChoiceMyopicPortfolioChoice(1)Whenislong-termportfoliochoiceequivalenttoshort-termportfo
4、liochoice,i.e.myopic?Assumepowerutility,lognormalassetreturns,approximateportfolioreturn(exactincontinuoustime)IPowerutilityinvestorsolvesamean-varianceproblemEasytoseethatiidreturnsimplymyopicinvestingwhennorebalancingispossibleIMeansandvariancesscalepr
5、oportionallytotheinvestmenthorizonISolutiontomean-varianceproblemisuna¤ectedbythehorizonTechnicaldi¢culty:portfolioreturnapproximationdeterioratesatlonghorizonsIButthishaslittleimpactinpractice(Barberis2000)Abiggerissue:Whatiftheinvestorcanrebalance?John
6、Y.Campbell(Ec2723)Long-TermPortfolioChoiceNovember20113/35MyopicPortfolioChoiceMyopicPortfolioChoice(2)Withpowerutility,portfoliochoicedoesnotdependonwealth,sopastreturnsirrelevantWithiidreturns,nostatevariablesSowecancon…neattentiontodeterministicportfo
7、liosharesWewanttoshowthatdeterministicαt=α,constantInvestorsolvesaK-periodmean-varianceproblem.ConsiderK=2.1γmaxEt(rp,2,t+2)+Vart(rp,2,t+2) Vart(rp,2,t+2).22JohnY.Campbell(Ec2723)Long-TermPortfolioChoiceNovember20114/35MyopicPortfolioChoiceMyopicPortfoli
8、oChoice(3)rp2,t+2 2rf=(rp,t+1 rf)+(rp,t+2 rf)12=αt(rt+1 rf)+αt(1 αt)σ212+αt+1(rt+2 rf)+αt+1(1 αt+1)σ,2Var(r)=(α2+α2)σ2tp,2,t+2tt+112Et(rp,2,t+2)+Vart(rp,2,t+2)=2rf+(αt+αt+1)(Er rf+σ/2).2JohnY.Campbell(Ec2723)Long-TermPortf