麻省理工行为金融学讲义 14127mtfrlc10pt1
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14.127Spring2004,Problem Set2Due:March18,2004,in class.Problem1.Optimism and Pessimism of PT Maximizers(17points) Tim owns a house in the Boston area.His company offered him a job in Europe that he accepted.In consequence,he decided to sell the house.He does not have much time,thus he just plan to post a take-it-or-leave-it offer at price x.For any price x∈[1;2]in millions of dollars,Tim assesses the probability q of closing the deal to equalq=2−xIf he doesn’tfind a buyer,he can always sell it to a friend for$1million.Tim is a Prospect Theory maximizer and he integrates over different accounts (house and money).In particular,he values any two-outcome distribution of changes to his reference point,say s with probability p and t with probability 1−p atV=v(t)+(v(s)−v(t))pwhenever s>t≥0or s<t≤0.Herev(z)=|z|1−γif z≥0and v(z)=−λ|z|1−γif z<0forγ∈(0,1)andλ>1.Tim’s reference point already includes all the changes required by the move to Europe other than the sale of the house.1.Assume that Tim is a pessimist and his reference point is based on pre-sumption that he sells the house for$1million.Thus,he will see it as a gain of x−1if he obtains x higher than pute the price x that Tim asks for as the function ofγandλ.2.Now,assume that Tim is an optimist and his reference point is based onpresumption that he sells the house for$2million.Thus,he will see any price x below this as a loss of2−pute the price x that Tim asks for as the function ofγandλ.3.Is there a difference between prices in questions1and2?For what pa-rameter values the price asked by optimistic Tim is higher than the price asked by pessimistic Tim?Try to explain the results intuitively.Problem2.Quick thought question.Bounded rationality(8points) Briefly describe and analyze(use less that1page,except if you have an interesting model)a real-world economic situations where bounded rationality matters.Bounded rationality is understood is the sense of cognitive limitations, as opposed to exotic tastes(like hyperbolic preferences)or erroneous beliefs(like overconfidence).Find an example that hasn’t been discussed in class.1Problem3.Big thought question.Try to solve one of the open problems mentioned during the course.(25points)For instance,attack one of the following questions:•Try to formulate an alternative to the Bayes rule.State and motivate it,explain what it explains(e.g.,insentitivity too some base rates)and potential limitations.•What are the regulatory implications of consumer confusion?•Where does confusionσεi comes from?For instance,provide a cognitive model that gives a microfoundation for this“noise”•Find a model that predicts the level of the confusionσ?e.g.,in the mutual fund market,give a model that predicts the reasonable order of magnitude.•Find a model that predicts howσvaries with experience?•How dofirms increase/create confusionσ?•Empirically,how could we distinguish whether profits come from true product differentiation,search costs,or confusion noise?•Devise a novel empirical strategy to measure an effect related to the ma-terial of lectures3to5.2。
行为金融学教学大纲一、课程概述行为金融学是金融学领域的一门重要分支,它将心理学和金融学相结合,研究在金融决策过程中,人类行为与心理因素的影响。
本课程旨在让学生理解行为金融学的基本概念、理论和方法,掌握行为金融学在实践中的应用,并能够运用行为金融学的原理来解释和理解现实金融市场中的现象。
二、课程目标1、掌握行为金融学的基本概念、理论和方法;2、理解人类行为和心理因素在金融决策中的作用;3、掌握行为金融学在实践中的应用;4、能够运用行为金融学的原理来解释和理解现实金融市场中的现象。
三、课程内容1、行为金融学概述:介绍行为金融学的概念、发展历程和基本理论;2、人类行为与金融决策:分析人类行为对金融决策的影响,包括认知偏差、情感因素等;3、心理账户与投资行为:探讨心理账户的概念、形成机制以及其对投资行为的影响;4、市场异象与行为金融:解释一些重要的市场异象,如过度反应、反应不足等,并分析其背后的行为金融学原理;5、行为投资策略:介绍基于行为金融学的投资策略,包括逆向投资、动量投资等;6、行为金融学的应用:探讨行为金融学在风险管理、资产定价等领域的应用;7、行为金融学的未来发展:介绍行为金融学未来的发展趋势和研究热点。
四、教学方法本课程将采用课堂讲解、案例分析、小组讨论等多种教学方法,以帮助学生更好地理解和掌握课程内容。
同时,还将邀请业内专家进行讲座,以增加学生对课程内容的兴趣和理解。
五、期末考核期末考核将采用论文或考试的形式,以检验学生对课程内容的掌握程度和理解深度。
具体形式将在课程开始前与学生进行说明和协商。
金融学教学大纲一、课程简介金融学是一门研究价值在不同主体之间转移和流动的学科。
它涵盖了众多领域,包括投资、风险管理、银行学、资本市场和公司财务等。
本课程旨在帮助学生理解金融学的基本概念、原理和工具,提高他们在金融领域的分析能力和决策能力。
二、课程目标1、掌握金融学的基本概念和原理,包括投资组合理论、资本资产定价模型、期权定价模型等。
《行为金融学》行为金融学的逻辑所导致的结论使人们去质疑传统金融学的大厦,而它的基本理论与我们已经接受的经济学的基本观念框架有着根本的分歧。
第一讲约翰·梅纳德·凯恩斯(1883-1946)“选美理论”《就业、利息和货币通论》每个参加者都从同一观点出发,于是都不选择他自己真认为最美者,也不选一般人真认为最美者,而是运用智力,推测一般人认为一般人所认为的最美者。
从社会观点看,要使得投资高明,只有战胜时间和无知的神秘力量,增加我们对未来的了解;但从私人观点,所谓最高明的投资,是先发制人,智夺群众,把坏东西让给别人。
“当别人贪婪时,我们要害怕;当别人害怕时,我们要贪婪。
”——沃伦.巴菲特巴菲特理财法:“三要三不要”要投资那些始终把股东利益放在首位的企业要投资资源垄断型行业要投资易了解、前景看好的企业不要贪婪不要跟风不要投机第一节对诺贝尔经济学奖你知道多少?1、世界上最著名的国际学术大奖——诺贝尔奖,每年12月10日在()举行授奖仪式2、下列各奖中,没有列入诺贝尔奖项是()A化学奖B物理奖C数学奖D和平奖3、诺贝尔奖从1969年起由5个奖项增加到6个,增设的奖项是()A经济科学奖B自然科学奖C社会科学奖诺贝尔经济学奖是1968年设立的,1969年首次颁奖,正式的名称是“艾尔弗雷德·诺贝尔经济学奖”,与其他奖项不同的是,该奖金不是来自诺贝尔的捐赠,而是来自瑞典中央银行。
首届获得者丁伯根有过精辟的评价:“人类幸福会受到经济政策的影响,而经济政策领先经济学形成它的洞察力。
”2001年美国经济学会(AEA)将该学会的最高奖克拉克(Clark Medal)颁给了加州大学伯克莱分校的马修拉宾,这是该奖项自1947年设立以来,首次授予给研究行为经济学的经济学家。
2002年,美国行为经济学家的代表人物——美国普林斯顿大学的丹尼尔·卡尼曼(Daniel Kahneman)和乔治梅森大学的弗农·史密斯(Vernonl Smith)获得当年的诺贝尔经济学奖。
行为金融学笔记行为金融学是金融学和心理学相结合的学科,它研究人们在金融决策中的行为和心理过程。
本文将介绍行为金融学的基本概念、主要理论模型以及在实践中的应用。
一、基本概念行为金融学的是人们在金融决策中的心理和行为过程,它认为人们的决策并不总是理性的,而是受到多种心理因素的影响。
这些心理因素包括认知偏差、情感、社会压力等。
行为金融学认为,这些心理因素会影响人们的判断和决策,从而影响金融市场的价格和交易量。
二、主要理论模型1、前景理论前景理论是行为金融学中最著名的理论之一,它是由Kahneman和Tversky提出的。
前景理论认为,人们在决策时会将问题分解成不同的阶段,每个阶段都有不同的价值函数。
价值函数描述了人们对于收益和损失的感受,它比传统的期望值理论更加准确地描述了人们的决策行为。
2、过度反应与反应不足过度反应是指人们在面对好消息或坏消息时,会做出过度的反应,导致市场价格偏离其基础价值。
反应不足则是指人们在面对坏消息时,会做出不足的反应,导致市场价格未能及时调整。
行为金融学认为,过度反应和反应不足是人们在金融决策中常见的心理现象。
3、羊群效应羊群效应是指人们在投资决策中会受到其他人的影响,跟随大众的行为。
当市场出现恐慌或狂热时,人们往往会跟随大众卖出或买入,导致市场价格偏离其基础价值。
行为金融学认为,羊群效应是导致市场波动的重要因素之一。
三、在实践中的应用行为金融学在实践中有广泛的应用,例如在投资策略、风险管理、市场监管等方面。
以下是几个例子:1、投资策略:行为金融学认为,投资者在决策时会受到心理因素的影响,因此可以采取一些策略来避免这些影响。
例如,通过反向投资策略(购买被低估的股票,卖出被高估的股票)来利用市场上的过度反应和反应不足。
还可以通过动量投资策略(跟随市场趋势)来利用市场上的羊群效应。
2、风险管理:行为金融学认为,人们在面对风险时可能会做出非理性的决策,导致风险增加。
因此,在风险管理方面,需要人们的心理过程,采取相应的措施来降低风险。
14.127Behavioral Economics(Lecture1)Xavier GabaixFebruary5,20031Overview•Instructor:Xavier Gabaix•Time4-6:45/7pm,with10minute break.•Requirements:3problem sets andTerm paper due September15,2004(meet Xavier in May to talk about it)2Some Psychology of Decision Making2.1Prospect Theory(Kahneman-Tversky,Econometrica79)Consider gambles with two outcomes:{with probability s,and|with probability13s where{D0D|.•Expected utility(EU)theory says that if you start with wealth Z then the(EU)value of the gamble isY=sx(Z+{)+(13s)x(Z+|)•Prospect theory(PT)says that the(PT)value of the game isY= (s)x({)+ (13s)x(|)where is a probability weighing function.In standard theory is linear.•In prospect theory is concavefirst and then convex,e.g.(s)=ss +(13s)for some M(0>1).Thefigure gives (s)for ==82.1.1What does the introduction of the weighing function mean?• (s)A s for small s.Small probabilities are overweighted,too salient.E.g.people play a lottery.Empirically,poor people and less educatedpeople are more likely to play lottery.Extreme risk aversion.• (s)?s for s close rge probabilities are underweight.In applications in economics (s)=s is often used except for lotteries and insurance2.1.2Utility function x•We assume that x({)is increasing in{,convex for loses,concave for gains,andfirst order concave at0that islim {<0+3x(3{)x({)= A1•A useful parametrizationx({)={ for{D0x({)=3 |{| for{$0•The graph of x({)for =2and ==8is given below2.1.3Meaning-Fourfold pattern of risk aversion x •Risk aversion in the domain of likely gains •Risk seeking in the domain of unlikely gains •Risk seeking in the domain of likely losses •Risk aversion in the domain of unlikely losses2.1.4How robust are the results?•Very robust:loss aversion at the reference point, A1•Robust:convexity of x for{?0•Slightly robust:underweighting and overweighting of probabilities (s)B s2.1.5In applications we often use a simplified PT(prospect theory):(s)=sandx({)={for{D0x({)= {for{$02.1.6Second order risk aversion of EU•Consider a gamble{+ and{3 with50:50chances.•Question:what risk premium would people pay to avoid the small risk ?•We will show that as <0this premium is R ³2´.This is calledsecond order risk aversion.•In fact we will show that for twice continuously di g erentiable utilities:( );=22>where is the curvature of x at0that is =3x00x0.•The risk premium makes the agent with utility function x indi g erent betweenx({)and 12x({+ + ( ))+12x({3 + ( ))•Assume that x is twice di g erentiable and take a look at the Taylor expansion of the above equality for small ..x({)=x({)+12x0({)2 ( )+14x00({)2h2+ ( )2i+r³2´or( )=2h2+ ( )2i+r³2´•Since ( )is much smaller than ,so the claimed approximation is true.Formally,conjecture the approximation,verify it,and usethe implicit function theorem to obtain uniqueness of the function defined implicitly be the above approximate equation.2.1.7First order risk aversion of PT•Consider same gamble as for EU.•We will show that in PT,as <0,the risk premium is of the order of when reference wealth{=0.This is called thefirst order risk aversion.•Let’s compute for x({)={ for{D0and x({)=3 |{| for {$0.•The premium at{=0satisfies0=12( + ( )) +12(3 )|3 + ( )|or( )= 1 311 +1=nwhere n is defined appropriately.2.1.8Calibration1•Take x(f)=f1313 ,i.e.a constant elasticity of substitution,CES,utility•Gamble1$50,000with probability1/2$100,000with probability1/2•Gamble2.${for sure.•Typical{that makes people indi g erent belongs to(60n>75n)(though some people are risk loving and ask for higher{.•Note the relation between{and the elasticity of substitution :{70n63n58n54n51=9n51=2n135102030Right seems to be between1and10.•Evidence onfinancial markets calls for bigger than10.This is the equity premium puzzle.2.1.9Calibration2•Gamble1$10.5with probability1/2$-10with probability1/2•Gamble2.Get$0for sure.•If someone prefers Gamble2,she or he satisfiesx(z)A 12x(z+ 3 )+12x(z+ + )=Here, =$=5and =$10=25.We know that in EU? W( )=2 2And thus with CES utility2Z?2forces large as the wealth Z is larger than105easily.2.1.10Calibration Conclusions•In PT we have W=n .For =2,and =$=25the risk premium is W=n =$=5while in EU W=$=001.•If we want tofit an EU parameter to a PT agent we getˆ =2nZand this explodes as <0.•If someone is averse to50-50lose$100/gain j for all wealth levels then he or she will turn down50-50lose O/gain J in the tableO\j$101$105$110$125 $400$400$420$550$1>250 $800$800$1>050$2>090" $1000$1>010$1>570"" $2000$2>320""" $10>000""""2.2What does it mean?•EU is still good for modelling.•Even behavioral economist stick to it when they are not interested in risk taking behavior,but in fairness for example.•The reason is that EU is nice,simple,and parsimonious.2.2.1Two extensions of PT•Both outcomes,{and|,are positive,0?{?|.Then,Y=y(|)+ (s)(y({)3y(|))=Why not Y= (s)y({)+ (13s)y(|)?Because it becomes self-contradictory when{=|and we stick to K-T calibration that puts (=5)?=5.•Continuous gambles,distribution i({)EU gives:Y=Z+"3"x({)i({)g{PT gives:Y=Z+"x({)i({) 0(S(j D{))g{+Z03"x({)i({) 0(S(j${))g{。
金融经济学10讲第一讲金融经济学的基本思想一、从数理经济学、数理金融学、数学(公理化方法)的关系瓦尔拉斯提出的一般均衡理论(1874),将一般经济均衡的观点数学化:考虑一个经济体中的参与者,他们可以被分为生产者和消费者两类;二者分别追求利润最大化和效用最大化;商品的供求关系通过价格调整达到均衡状态;由于商品的供求都是价格的函数,因此均衡价格意味着在这一价格体系下,供给等于需求;通过求解方程组可以得到一组均衡价格。
尽管瓦尔拉斯给出一般均衡的线性方程组过于浅显,但其思想确是数理经济学的开端;他的后继者通过引入更为高深的数学工具,从而更为严格的讨论了宏观经济学中的一般均衡问题,其中最为著名的是阿罗和德布鲁(1954年,一般均衡的存在性的证明)。
可以看出:数学方法在处理经济问题中所显示的强大威力,为什么?其根源是数学的严格性、逻辑性;经济问题与纯数学有很大差异,但其内在的逻辑性仍需要数学方法去揭示。
数学本身是一种“语言”,没有语言,我们无法说清楚所研究的问题。
金融学中的问题与经济学中的问题有所不同,前者关注的对象是金融资产(工具),后者关注的则是一般的商品。
投资者买卖金融资产的主要目的是盈利,而买入商品的主要目的是消费,这导致了数理经济学的一般方法在处理金融问题时需要修正。
马科维茨(1952)提出的投资组合理论是现代金融理论的开端,它首先明确了金融资产的两个基本特征:风险、收益;并指出:投资者的总是在二者之间作出权衡。
其学生夏普(1964)提出了著名的资本资产定价模型,首次给出了令人信服的金融资产定价方法。
此后的金融学朝着微观金融的方向发展,其核心是资产的定价问题(还有一些派生的问题,如风险管理问题),较为著名的理论有:罗斯(1976)的套利定价理论、公司财务的MM定理、法玛的有效市场理论、布莱克-肖尔斯的期权定价理论。
这些理论构成了金融经济学的主要内容。
什么是公理化方法?这个概念来源于数学,数学中的每个分支都是从一些不能证明的公理出发的,如平面几何中的公理;数学中的定理是在公理的基础上进行逻辑证明后的结论;承认公理的正确性,就必须承认定理的正确性。
行为金融学都讲了什么?(1)2017年诺贝尔经济学奖终于揭晓了。
10月9日,瑞典皇家科学院宣布将2017年诺贝尔经济学奖授予美国经济学家理查德·泰勒(RichardThaler),表彰其在行为经济学领域的贡献。
以往诺奖表彰的经济研究成果似乎相对“高大上”,而泰勒的行为经济学和行为金融学则更为“接地气”,更贴近大众生活。
这究竟是门怎样的学问呢?最近小白也在学行为金融学这门课,在接下来的几期文章中,我就跟大家严肃地科普一下行为金融学这门学科究竟讲了啥。
What is Behavior Finance?--何为行为金融学传统经济学认为,人是绝对理性的。
但是很明显,不是所有的人都是谢耳朵。
2 0世纪80年代以后,大量的心理学和行为学证据显示:人并非都是理性的,在面临未来的不确定性时,人们往往会偏离假设的理性行为模式。
行为金融理论(Behavior Finance)由此应运而生。
行为金融学就是将心理学尤其是行为科学的理论融入到金融学之中,从微观个体行为以及产生这种行为的心理等动因来解释、研究和预测金融市场的发展。
千万不要以为行为金融学就是散户投资心理学。
生而为人,就注定会犯错误,机构,庄家,即便是巴菲特这样的投资天才也概莫能外。
Cognitive Errors--人们常见的认知错误人为什么会出现认知错误?经济学家认为,大脑通常采用简单的推理方式应对复杂环境,或是推理过程缺乏足够的统计分析,因此出现偏差在所难免。
犯错并不可怕,可怕的是意识不到自己在犯错。
行为金融学可以帮助我们发现这些细小的错误念头,并及时纠正自己。
常见的认知错误可分为两类:Believe Perseverance and Processing Errors,固执己见和信息处理谬误。
今天主要介绍第一类。
1.Believe Perseverance固执己见的表现主要有以下5种:1)Conservatism Bias 保守性偏差这种偏差指的是人们一旦对事物形成了最初的印象,便很难修正原有的观点,即便有了新的信息也会反应不足。
Wealth Accumulation, Credit Card Borrowing,and Consumption-IncomeComovementDavid Laibson,Andrea Repetto,andJeremy TobacmanCurrent Draft:March2002Self-reports about saving.²Consumers report a preference for°at or rising consumption paths.²Baby boomers report median target savings rate of15%.²Actual median savings rate is5%.²76%of household's believe they should be saving more for retirement(Public Agenda,1997).²Of those who feel that they are at a point in their lives when they\should be seriously saving al-ready,"only6%report being\ahead"in their saving,while55%report being\behind."Further evidence:Normative value of commitment.²\Use whatever means possible to remove a set amount of money from your bank account each month before you have a chance to spend it."²Choose excess withholding.²Cut up credit cards,put them in a safe deposit box,or freeze them in a block of ice.²\Sixty percent of Americans say it is better to keep,rather than loosen legal restrictions on re-tirement plans so that people don't use the money for other things."²Social Security and Roscas.²Christmas Clubs(10mil.accounts).1Consumption-Savings Behavior²Substantial retirement wealth accumulation(SCF)²Extensive credit card borrowing(SCF,Fed,Grossand Souleles2000,Laibson,Repetto,and Tobac-man2000)²Consumption-income comovement(Hall and Mishkin 1982,many others)²Anomalous retirement consumption drop(Bankset al1998,Bernheim,Skinner,and Weinberg1997)2 Data²Three moments on previous slide(wealth,%Visa, mean Visa)from SCF data.Correct for cohort, household demographic,and business cycle ef-fects,so simulated and empirical hh's are pute covariances directly.²C-Y from PSID:¢ln(C it)=®E t¡1¢ln(Y it)+X it¯+"it(1)²C drop from PSID¢ln(C it)=I RETIREit°+X it¯+"it(2)²"A Debt Puzzle":only"%Visa"and"wealth"²"JEP paper":add"liquid share"and"%low liquid wealth"Table 1. Credit Card Debt a,bConditional on Having a Credit CardBalance% with Card% with Debt Mean Median All categories20-290.720.771668746 30-390.770.762114772 40-490.850.722487760 50-590.840.601603343 60-690.830.43980070+0.800.272500 All ages0.800.631715343 No high school diploma20-290.680.831823849 30-390.660.772559943 40-490.770.842988815 50-590.730.711910549 60-690.710.55111512970+0.760.352850 All ages0.720.681832429 High school graduates20-290.600.841885935 30-390.740.861673858 40-490.810.732274772 50-590.840.721424515 60-690.850.44722070+0.750.282650 All ages0.770.701537472 College graduates20-290.890.651364600 30-390.920.652213532 40-490.930.642340497 50-590.960.401545060-69 1.000.261143070+0.930.131800 All ages0.930.53176794 Source: Authors' calculations based on the 1995 SCF.a Includes traditional cards such as Visa, Mastercard, Discover and Optima, and other credit or charge cards such as Diners Club, American Express, store cards, airline cards, car rental cards, and gasoline cards.Excludes business and company cards.b The total credit card debt is constructed on the basis of theresponses to the following SCF question:"After the last payments were made on this (these) account(s),roughly what was the balance still owed on this (these) account(s)?"Table 2. Fraction of Households Borrowing on Credit Cards Acrossthe Distribution of Wealth a,bWealth Distribution Percentile Age group Less than 2525-5050-75Over 75 All categories20-290.870.770.700.6530-390.860.800.690.5140-490.790.760.560.4150-590.750.650.400.2760-690.550.400.250.1870+0.480.260.110.05 Incomplete High School20-290.910.830.670.8230-390.730.820.780.7040-490.840.850.800.6050-590.830.670.750.4560-690.600.510.390.2570+0.570.300.240.10 High School Graduates20-290.890.780.820.7330-390.900.830.830.6640-490.860.790.740.5050-590.790.720.550.4060-690.600.420.310.2470+0.470.290.090.14 College Graduates20-290.810.650.510.5630-390.820.610.550.3940-490.710.530.440.2050-590.630.380.240.2260-690.410.200.090.1070+0.280.070.060.03 Source: Authors' calculations based on the 1983-1995 SCFs.a Conditional on having a credit card.b We calculated the fraction of households who are borrowing in each quartile of the wealth distribution contingent on age and education group, for every SCF year. The table reports the weighted average across the 4 SCF years, using the proportion of households with credit cards in a given year/category as weights.3Digression:Model-building3.1Why do people save?3.2Why do people borrow on credit cards?4Model²Recent consumption papers use simulations²Rich environments,eg with income uncertaintyand liquidity constraints²Literature pioneered by Carroll(1992,1997),Deaton (1991),and Zeldes(1989)²Gourinchas and Parker(2001)use method of sim-ulated moments(MSM)to estimate a structuralmodel of life-cycle consumption4.1Demographics²Mortality,Retirement(PSID),Dependents(PSID), HS educational group4.2Income from transfers and wages²Y t=after-tax labor and bequest income plus govttransfers(assumed exog.,calibrated from PSID)²y t´ln(Y t):During working life:y t=f W(t)+u t+ºW t(3)²During retirement:y t=f R(t)+ºR t(4)4.3Liquid assets and non-collateralized debt ²X t+Y t represents liquid asset holdings at the beginning of period t:²Credit limit:X t¸¡¸¢¹Y t²¸=:30;so average credit limit is approximately $8,000(SCF).²Liquid asset aftertax interest rate:2%,3%,3.75%²Credit card interest rate:9%,10%,11.75%4.4Illiquid assets²Z t represents illiquid asset holdings at age t:²Z bounded below by zero.²Z generates consumption°ows each period of °Z;set°=5%,6%,7%²Conceive of Z as having some of the properties of home equity.²Disallow withdrawals from Z;Z is perfectly illiquid.²Z stylized to preserve computational tractability.Z is perfectly illiquid;withdrawals from Z are disal-lowed.1.House of value H,mortgage of size M.2.Consumption°ow of°H;minus interest cost of°´M;where´=i¢(1¡¿)¡:3.°¼´=)net consumption°ow of°H¡´M¼°(H¡M)=°Z:We've explored di®erent possi-bilities for withdrawals from Z before..4.5Time Preferences²Discount function:f1;¯±;¯±2;¯±3;:::g²¯=1:standard exponential discounting case ²¯<1:preferences are qualitatively hyperbolic ²Null hypothesis:¯=1T X¿=t+1±¿u(C¿)(5) U t(f C¿g T¿=t)=u(C t)+¯In full detail,self t has instantaneous payo®functionu (C t ;Z t ;n t )=n t ¢³C t +°Z t n t ´1¡¡11¡and continuation payo®s given by:¯T +N ¡t Xi =1±i ³¦i ¡1j =1s t +j ´(s t +i )¢u (C t +i ;Z t +i ;n t +i ):::+¯T +N ¡t X i =1±i ³¦i ¡1j =1s t +j ´(1¡s t +i )¢B (X t +i ;Z t +i )²n t is e®ective household size:adults+(.4)(kids)²°Z t represents real after-tax net consumption °ow ²s t +1is survival probability²B (¢)represents the payo®in the death state°°4.6Computation²Dynamic problem:u(C t;Z t;n t)+¯±E t V t;t+1(¤t+1)maxI X t,I Z ts:t:Budget constraints²¤t=(X t+Y t;Z t;u t)(state variables)²Functional Equation:V t¡1;t(¤t)=f s t[u(C t;Z t;n t)+±E t V t;t+1(¤t+1)]+(1¡s t)E t B(¤t)²Solve for eq strategies using backwards induction²Simulate behavior²Calculate descriptive moments of consumer be-havior5EstimationEstimate parameter vectorµand evaluate models wrt data.²m e=N empirical moments,VCV matrix=-²m s(µ)=analogous simulated moments²q(µ)´(m s(µ)¡m e)-¡1(m s(µ)¡m e)0,a scalar-valued loss function²Minimize loss function:^µ=arg minµq(µ)²^µis the MSM estimator.²Pakes and Pollard(1989)prove asymptotic con-sistency and normality.²Speci¯cation tests:q(^µ)»Â2(N¡#parameters)6Results²Exponential(¯=1)case:^±=:857§:005;q³^±;1´=512²Hyperbolic case:(^¯=:661§:012^±=:956§:001q³^±;^¯´=75 (Conservative case:h R X;°;R CC i=[1:0375;0:05;1:1175 Punchlines:²¯estimated signi¯cantly below1.²Reject¯=1null hypothesis with a t-stat of25.²Speci¯cation tests reject both the exponential andthe hyperbolic models.Robustness: Aggressive:h R X;°;R CC i=[1:02;0:07;1:09] Intermediate:h R X;°;R CC i=[1:03;0:06;1:10] Conservative:h R X;°;R CC i=[1:0375;0:05;1:1175]7Conclusion²Structural test using the method of simulated mo-ments rejects the exponential discounting null.²Speci¯cation tests reject both the exponential and the hyperbolic models.²Quantitative results are sensitive to interest rate assumptions.²Hyperbolic discounting does a better job of match-ing the available empirical evidence on consump-tion and savings.。