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1、Introduction to Behavioral Economics 行为经济学行为经济学方向博士方向博士Oklahoma State University参考书 作者: 孙惟微：独立经济学者，策略顾问、熙代（北京）文化传媒有限公司执行董事。 董志勇 (作者) 丹丹艾瑞里艾瑞里 A Short Survey Focusing for now on individual decisions, what does mainstream (standard neoclassical) economics normally assume?Assumptions Rationality 无限理性:
2、Is perfectly rational, making choices that consistently maximize some exogenous, stable set of preferences that depend on absolute levels of outcomes (rather than changes). 经济学假设个人具有经济学假设个人具有稳定和连续的偏好，并用无限理性使这些偏好最大化稳定和连续的偏好，并用无限理性使这些偏好最大化 Self-Interest无限自私自利: Is almost always also assumed to be perfe
3、ctly self-interested, caring exclusively about her/his own consumption, though this assumption is not essential to mainstream theory. Self-Control无限意志力: Has perfect will-power and the ability to make and follow intertemporal plans (even contingent ones), with no conflict between the preferences of c
4、urrent and future selves. 而行为经济学正是基于对以上三个“无限性”的反对提出了自己关于非理性人的新观点1。正常生活中的经济个体应该是非理性的，这样一个非理性的人，并不具备稳定和连续的偏好以及使这些偏好最大化的无限理性；2。即使知道效用最大化的最优解也有可能因为自我控制意志力方面的原因而无法做出相应的最优决策；3。其经济决策的过程中包含了相当的非物质动机和非经济动机权重，人们会愿意牺牲自己的利益去帮助他人。行为经济学的兴起主要有三方面的原因行为经济学的兴起主要有三方面的原因第一是基于对精神心理因素的研究。现代经济学向心理学靠拢,同现代经济中的精神心理因素有关，与现代经济
5、的日益“非物质化”、“商品的个性化”有关。 第二，行为经济学拓宽了正统经济学的领域。经济学家一向认为人是理性的动物，即人总是倾向于追求最大收益或承担最小成本。但人类行为固然有其理性一面，也有其非理性的一面。所以，非理性行为可用科学的方法加以研究。 (“不买最好的，只买最贵的。”) 第三，传统经济学认为，经济学是一门研究财富的学问；而现代经济学提出，经济学也是一门研究人的学问。人类社会化的行为受复杂的社会关系制约，从而导致人的行为选择并非都是建立在理性思考的基础上。因此从纯理性研究人的行为行不通。从经济主体讲，经济过程最终体现为人的经济行为过程，因而对人的分析离不开用人的心理对其行为的解释。亚当
6、斯密 Adam Smith 每个人都力求运用自己的资本，生产出最大的价值。一般而来，他不会为了促进公共利益，也不知道促进多少。他只考虑自己的安全，自己的所得。正是这样，他由一只看不见的手引导着，实现着他自己并不打算实现的目标。 与有意地促进相比， 在追求他自己得利益的过程中，往往能够更加有效地促进社会得公益。 直到最近，经济学尚被普遍看作一种必须依赖于对现实世界的观察、而不能依靠在实验室里做受控制的实验来进行研究的非实验性科学。许多评论者发现受利己主义和理性决策所支配的“经济人”(homo oeconomicus)这一普遍假设存在局限性。然而，经济学研究已经开始朝着新的方向起飞。大量和日益增多
7、的科学工作致力于对经济学传统的基本假设的经验检验和修改，特别是有关无限理性、纯粹利己主义和完全自治的假设。 而且，目前的研究越来越依赖于来自实验室的新的实验数据，而不是从对实际经济的观察中所得到的传统的现场数据。最近的这些研究源于两个区别显著、但正趋于一致的传统：一是认知心理学中有关个人决策的理论和经验研究；二是以实验的方法对经济理论预言的检验。行为经济学和实验经济学已经跻身于经济学最活跃的领域之列。2002的诺贝尔经济学奖得主就是在这两个领域从事研究的前辈。2002: Vernon Smith and Daniel Kahneman received the Nobel Prize Vern
8、on Smith: “for the use of laboratory experiments as a tool in empirical economic analysis, in particular, for the study of different market mechanisms.” Founder of experimental economics. Daniel Kahneman: “for the introduction of insights from psychological research into economics, in particular wit
9、h regard to judgments and decisions under uncertainty.” Kahnemans research is based on psychological experiments and questionnaires. Founder of behavioral economics.实验经济学 传统上，经济学被看作一种完全依赖现场数据的非实验性科学。许多人认为，这一点是经济学作为一门科学继续发展的障碍。除非我们可以进行受控制的实验，否则对经济理论的检验将永远是有限的。仅仅根据现场数据，人们很难判断一个理论是否失败或何时失败，并正确地指出失败的原因。
10、在理论与受控制的实验观察两者之间的反馈渠道在经济学中基本不存在。 一种新兴的、被称作“实验经济学”的研究领域的建立从根本上对这一观点提出了挑战。在受控制的实验室里，实验者以简单、抽象的形式模仿在市场和其他经济交往形式中出现的场景，以研究这些场景中的人类行为。实验经济学的历史 早年已有前辈学者从事经济学的实验研究。50多年前，张伯伦(Chamberlin，1948)试图通过实验来检验新古典的完全竞争理论。 约翰纳什(John Nash)1994年诺贝尔经济学奖得主与他的同事通过设置一个实验对博弈论的预测能力进行了早期研究。 弗农史密斯在亚利桑那大学十一个班级进行了长达六年的实验，验证了竞争均衡理
11、论。据此实验所撰写的论文竞争市场行为的实验研究在1962年的政治经济学杂志发表，标志着实验经济学的诞生。 弗农史密斯的意义最重大的工作涉及市场机制。他对竞争性市场所做的创新性实验 (1962)、对不同拍卖形式的检验(1965，1976，1980)，以及对“诱导价值法”(induced-value，1976)的设计，都为这一领域的研究奠定了基础。 查尔斯普洛特认为：“实验室建立的经济与现实经济相比可能特别简单，但是却一样地真实。真实的人被真实的金钱所驱动，因为真实的天赋和真实的局限，作出真实的决策和真实的错误，并为其行为后果而真实地悲喜”。History of Behavioral Econom
12、ics行为经济学历史 Adam Smith, who is best known for the concept of the invisible hand and The Wealth of Nations, wrote a less well-known book The Theory of Moral Sentiments (道德情操论 ), which laid out psychological principles of individual behavior that are arguably as profound as his economic observations. F
13、or example, Adam Smith commented (1759/1892, 311) that we suffer more. when we fall from a better to a worse situation, than we ever enjoy when we rise from a worse to a better.” Loss aversion! 损失厌恶认知心理学的发展 Beginning around 1960, cognitive psychology became dominated by the metaphor of the brain as
14、an information-processing device replacing the behaviorist conception of the brain as a stimulus-response machine. The information-processing metaphor permitted a fresh study of neglected topics like memory, problem solving and decision making. These new topics were more obviously relevant to the ne
15、oclassical conception of utility maximization than behaviorism had appeared to be.Herbert Simon 西蒙 现代决策理论的奠基人 卡内基大学教授西蒙， 心理学家和人工智能的创立者 批判理性经济人的假设， 提出 “有限理性” (bounded rationality) 概念, 获得1978年诺贝尔奖。 西蒙指出了新古典经济学理论的不现实之处，分析了它的两个致命弱点：(1)假定目前状况与未来变化具有必然的一致性；(2)假定全部可供选择的“备选方案”和“策略”的可能结果都是已知的。 有限理性 人的有限性包括两个
16、方面的含义，一是环境是复杂的，在非个人交换形式中，人们面临的是一个复杂的、不确定的世界，而且交易越多，不确定性就越大，信息也就越不完全；二是人对环境的计算能力和认识能力是有限的，人不可能无所不知。 西蒙认为,人们在决定过程中寻找的并非是“最优”的标准，而只是“满意”的标准。 Tversky and Kahneman Perhaps the two most influential contributions were published by Tversky and Kahneman. Their 1974 Science article argued that heuristic short
17、-cuts created probability judgments which deviated from statistical principles. (Amos Tversky and Daniel Kahneman, “Judgment under Uncertainty: Heuristics and Biases,” Science 185 (1974), pp. 1124 1131) Their 1979 paper Prospect theory: decision making under risk documented violations of expected ut
18、ility and proposed an axiomatic theory, grounded in psychophysical principles, to explain the violations. It was published in the technical journal Econometrica and is one of the most widely cited papers ever published in that journal.Steps that early BE research tookFirst, identify normative assump
19、tions or models that are ubiquitously used by economists, such as Bayesian updating, expected utility and discounted utility. Second, identify anomaliesi.e., demonstrate clear violations of the assumption or model, and painstakingly rule out alternative explanations (such as subjects confusion or tr
20、ansactions costs). Third, use the anomalies as inspiration to create alternative theories that generalize existing models. A fourth step is to construct economic models of behavior using the behavioral assumptions from the third step, derive fresh implications, and test them.例子1A.你一定能赚30000元。 B.你有80
21、%可能赚40000元，20%可能性什么也得不到。例子2A.你一定会赔30000元。 B.你有80%可能赔40000元，20%可能不赔钱。例子3假设你面对这样一个选择：在商品和服务价格相同的情况下，你有两种选择： A.其他同事一年挣6万元的情况下，你的年收入7万元。 B.其他同事年收入为9万元的情况下，你一年有8万元进账。 认知心理学家考虑的是一个交互作用的过程，几个因素都会对决策产生重要影响，比如知觉、信仰或心智模式。诸如感情、态度等内在动机也会影响一项决策。此外，对以前决策及其后果的记忆是一个至关重要的认知函数。在这种复杂观点下，人类行为被认为是局部地适应于一个既定的环境。行为具有适应性，取
22、决于环境和瞬间的感知状态。 卡尼曼等人通过调查和实验收集到的事实，对经济学的理性假设，至少是对复杂决策情景下的理性假设提出了质疑。例如，现实世界中的决策者不总是依据概率法则评价不确定前景，有时，制定决策会违背预期效用最大化原则。卡尼曼的贡献主要是关于不确定条件下的判断和决策。 阿莫斯特维尔斯基(Amos Tversky) ，丹尼尔卡尼曼(Daniel Kahneman) ，里查德萨勒(Richard H. Thaler) ，马修拉宾(Matthew Rabin) ，美籍华人奚恺元教授等是这一学科的开创性代表。总结丹尼尔卡尼曼运用认知心理学中关于心理过程的深刻见解，帮助我们更好地理解了人们制定经
23、济决策的行为。卡尼曼和特维尔斯基对不确定条件下决策行为的研究最有影响力。卡尼曼还对行为经济学等其他领域作出了开创性的贡献。卡尼曼已经成为近期在行为经济学和金融学研究领域中所出现的繁荣景象背后的一个主要灵感来源。他的研究对其他领域也产生了重大影响。 弗农史密斯是开创以实验作为经济学经验方法论的一个最有影响的人物。与卡尼曼不同，他没有以挑战传统经济学理性决策理论而开始，而是检验了关于市场表现的假说。卡尼曼的调查和实验主要关注个人的决策，而史密斯则将实验的重点放在特定市场环境下人与人之间的相互作用上。他还强调了方法论问题，发展了具有实践性的实验方法，建立了构筑一个良好实验的标准。基于史密斯的成就，许
24、多经济学家开始把实验室实验作为一个基本工具。 Main Topics 前景理论 (Prospect Theory) 启发式与偏差 (Heuristics and Biases) 锚定理论和现状偏见 (Anchoring and Adjustment, Status Quo Bias) 禀禀赋效应 (Endowment Effect) 偏好理论 (Preference Reversal) 时间贴现和跨期选择 (Time Discounting and Time Preference) 心理帐户 (Mental Accounting) 其他应用Example: Status Quo Bias 现状
25、偏见Decision-makers have an overwhelming tendency to adopt defaults, to stick with the status quoEven when the decision is important and the stakes are large Even when the decision-maker is told that the default is suboptimal Examples from 401(k) plans: participation, savings rate, asset allocation (c
26、ompany stock). Other examples: insurance deductibles, organ donationBrigitte Madrian and Dennis Shea (2001) Design: A Fortune 500 Company Switched 401(k) default on April 1, 1998. Madrian and Shea examine behavior of new hires. OLD Default Contribution: Must actively sign up Default Allocation: None
27、 NEW Default Contribution: 3 percent of compensation deducted for plan Default Allocation: Money Market Fund401(k) Participation IncreasesPercent at Specified Contribution RateSource: Madrian and Shea (2001). Contribution Rate401(k) Asset Allocation Also ChangedSource: Madrian and Shea (2001). Perce
28、nt of AssetsImpact of Automatic Enrollment in 401(k) Before, During and AfterSource: Choi, Laibson, Madrian, Metrick (2004)Policy Application: Pension Reform Bill of 2006The 900-page Pension Protection Act of 2006 comes as the number of people covered by a defined-benefit pension has steadily declin
29、ed and awareness has grown about the lack of adequate savings among Americans.A majority of workers 45 and older have less than $50,000 in savings, according to a survey by the Employee Benefit Research Institute (EBRI). Whats more, almost 40 percent of workers over 40 dont participate in a 401(k) w
30、hen they are eligible.The new legislation encourages companies to automatically enroll 401(k)-eligible employees and to automatically increase worker contributions every year. It also allows the plan provider chosen by the employer to offer investment advice to workers. Automatic enrollment is expec
31、ted to boost the participation rate in 401(k) plans beyond 90 percent.By Jeanne Sahadi, CNNMLibertarian-Paternalism:Set the default to help people, but they can opt out. “不满意七天可以退货”的商品; 汽车行也会借车给人试驾。 为救美国经济于水深火热，美联储主席伯南克有句名言：“如有必要，可用直升机撒钱。” 意外之财 地王Introduction to Lab ExperimentsLab Experiments“One po
32、ssible way of figuring out economic laws . is by controlled experiments. . Economists (unfortunately ). cannot perform the controlled experiments of chemists or biologists because they cannot easily control other important factors. Like astronomers or meteorologists, they generally must be content l
33、argely to observe.” (Samuelson and Nordhaus, 1985, p. 8)“Economic Theory, through a formal deductive system, provides the basis for experimental abstraction and the experimental design, but society in most cases carries out the experiment, . Therefore, the economic researcher observes the outcome of
34、 societys experiment or performance but has little or no impact on the experimental design and the observations generated. Thus, by the passive nature of the data, economic researchers are, to a large extent, restricted in their knowledge search to the process of nonexperimental model building. . th
35、e experiment is outside the researchers control.”( “The Nonexperimental Model- Building Restriction” in Judge et al. (1988)Philosophy of science: the scientific methodPhilosophy How we understand the worldScience A “method” for achieving this goal Development of theory Formulation of hypotheses - pr
36、edictions Tests of predictionsDesign & Analysis How we test predictions of hypothesesStatistics Tool for quantitative testsScienceAssumptions Realism World is subject to investigation Rationalitylogic Regularity Results can be generalized Causalityworld is ordereddeterminism Discoverability or knowa
37、bility of causesDefinitionsInduction (or inductive reasoning): reasoning that general laws exist because particular cases that seem to be examples of it existDeduction (or deductive reasoning): reasoning that something must be true because it is a particular case of a general (universal) law known t
38、o be trueInductionspecific generaldeduction5 swans seen, all are white all swans are whiteTypes of Research Design Three traditional categories:ExploratoryDescriptiveCausal The choice of the most appropriate design depends largely on the objectives of the research and how much is known about the pro
39、blem and research objectives.Basic Research Objectives and Research DesignResearch ObjectiveAppropriate DesignTo gain background information, Exploratoryto define terms, to clarify problems and hypotheses, to establish research prioritiesTo describe and measure marketing Descriptivephenomena at a po
40、int in timeTo determine causality, Causalto make “if-then” statementsExploratory Research Exploratory research is most commonly unstructured, informal research that is undertaken to gain background information about the general nature of the research problem. By unstructured, we mean there is no for
41、mal set of objectives, sample plan, or questionnaire.Exploratory Research It is usually conducted when the researcher does not know much about the problems. Exploratory research is usually conducted at the outset of research projects.Exploratory Research Uses Gain Background Information Define Terms
42、 Clarify Problems and Hypothesis (refine research objectives) Establish Research PrioritiesMany questions; many sourcesDefining the problem; getting a “feel”Exploratory Research A variety of methods are available to conduct exploratory research.Secondary Data AnalysisExperience SurveysCase AnalysisD
43、escriptive Research Descriptive research is undertaken to describe answers to questions of who, what, where, when, and how. Descriptive research is desirable when we wish to project a studys findings to a larger population, if the studys sample is representative.Causal Research Causality may be thou
44、ght of as understanding a phenomenon in terms of conditional statements of the form “If x, then y.” Causal studies are conducted through the use of experiments.Experiments An experiment is defined as manipulating an independent variable to see how it affects a dependent variable, while also controll
45、ing the effects of additional extraneous variables.Example: Our Proposition Hypothesis: Southern white males are more prone to aggression than are Northern white males. (conjecture) Well look at different strategies to examine hypotheses. (refutation)Refutation putting theories to the test What evid
46、ence supports (and, more importantly, disconfirms) our theories?Descriptive Research assesses the amount or average level of a given variable in a population e.g., public opinion surveys not a true test of an hypothesis What is the white male homicide rate in the South?Descriptive Research What is t
47、he white male homicide rate in the South?adapted from Nisbett (1993)Descriptive Research critical issues random sampling basis of comparison informative, but not a hypothesis test What else could account for the findings?Correlational Research investigates whether changes in one variable are related
48、 to changes in another variable What is the relationship between being from the South and aggressive behavior?Correlational Research correlation coefficients range from +1.00 to -1.00 positive correlation: increase/decrease in the same directionCorrelational Research0123456701234567Correlational Res
49、earch correlation coefficients range from +1.00 to -1.00 negative correlation: increase/decrease in opposite directionsCorrelational Research0123456701234567Correlational Research correlation coefficients range from +1.00 to -1.00 strength of the relationship: closeness to +1.00/-1.00, not by the va
50、lence (+/-) Which indicates a stronger correlation: -.74 or +.21?Correlational Research0123456701234567Correlational Research What is the relationship between being from the South and aggressive behavior? Nisbett (1993) homicide rate and “southernness”:rs = .37 in the social sciences (Cohen, 1992) r