《高级微观经济学》PPT课件.ppt

Chapter Four,Utility 效用,关于偏好的题外话,“要设计一个有效的激励机制，前提就是如何理解人们的偏好。” 当人力资源主管在建立各种各样的激励机制时，必须能够预见到激励对象对此会做出怎样的反映，无论是设计薪酬制度，还是出台招聘、解雇、职称、职位、工作环境等政策，只有深入理解他们的偏好，才能找到符合企业发展需求的最优方案。 风险补偿激发动力 “正因为一个人工作需要付出成本，所以要给予补偿，也正因为他在乎收入，所以我们才可以调动他的积极性，才有办法监督、制约他。” 张维迎,偏好题外话,从这些简单的假定中，一名合格人力资源主管应该至少可以读出薪酬激励的三种含义： 一是工资水平必须随着工作量的增加而递增。当工作量、工作时间、努力程度等工作成本不断增加时，多出部分的工资率一定要相应越来越高，通常加班费高于正常工资就是这个道理。 二是收入越高激励成本也就越高。收入水平越高，要调动其积极性就越困难。如果招聘对象拥有的财富越多，企业为他提供的预期收入也就应该越高。 三是确定的收入和不确定的风险收入不是等价的，承担风险越大的人需要得到的补偿越多。,偏好题外话,奖惩激励善用心理 “但在某些情况下，传统经济学的上述假设并不能准确地反映出人们的偏好，以及每个人是怎样决策的。” 以色列心理经济学家丹尼尔卡尼曼对偏好的假设有所不同，正因在“研究不确定状态下人们如何作出判断和决策”方面作出的突出贡献，卡尼曼和另一位实验经济学家共同摘取了2002年诺贝尔经济学奖的桂冠。 卡尼曼的理论可以用来解释很多传统经济学理论无法解释的问题。传统经济学研究一般假定人们出于自身利益的驱动能够作出理性决策，而卡尼曼通过运用感知心理学分析法研究人类的分析决策行为得出：人的心理其实非常复杂，当所得的比预期的多时，人们会非常高兴，而当失去的比预期的多时就会非常愤怒痛苦，关键在于这两种情绪是不对称的，人们在失去某物时愤怒痛苦的程度远远超过得到某物时高兴的程度。,效用的含义,消费行为理论中的理性假定 消费者行为理论中理性假定通常是其出发点。消费者被假定在可供选择的商品中，按照从消费商品中得到尽可能的方式中进行选择。这意味着消费者有各种选择，并且能对这些选择进行评价。 与消费者从各种不同数量商品取得的满足有关的全部信息，都包含在他的效用函数中。 效用和效用函数与任何意义上的美学无关。 基数效用论的代表人物： 19世纪的杰文斯、瓦尔拉斯、马歇尔。,Structure,Utility function （效用函数） Definition（定义） Monotonic transformation （单调变换） Examples of utility functions and their indifference curves（例子） Marginal utility （边际效用） Marginal rate of substitution 边际替代率 MRS after monotonic transformation,Utility Functions,A utility function U(x) represents a preference relation if and only if: x x” U(x) U(x”) x x” U(x) U(x”) x x” U(x) = U(x”).,p,p,Utility Functions,Utility is an ordinal 顺序的(i.e. ordering) concept（序数概念）. E.g. if U(x) = 6 and U(y) = 2 then bundle x is strictly preferred to bundle y. But x is not preferred three times as much as is y.（效用虽然能够表示大小绝对值，但偏好则不能？）,Utility Functions & Indiff. Curves,Consider the bundles (4,1), (2,3) and (2,2). Suppose (2,3) (4,1) (2,2). Assign to these bundles any numbers that preserve the preference ordering; e.g. U(2,3) = 6 U(4,1) = U(2,2) = 4. Call these numbers utility levels.（这些数字则表示效用水平）,p,Utility Functions & Indiff. Curves,An indifference curve contains equally preferred bundles. Equal preference same utility level. （相同的偏好=相同的效用水平） Therefore, all bundles in an indifference curve have the same utility level.（因而，无差异曲线上的所有消费束表示相同的效用水平。）,Utility Functions & Indiff. Curves,So the bundles (4,1) and (2,2) are in the indiff. curve with utility level U 4 But the bundle (2,3) is in the indiff. curve with utility level U 6. On an indifference curve diagram, this preference information looks as follows:,Utility Functions & Indiff. Curves,U 6,U 4,(2,3) (2,2) (4,1),x1,x2,p,Utility Functions & Indiff. Curves,Comparing more bundles will create a larger collection of all indifference curves and a better description of the consumers preferences. （比较更多的消费束，将获得更大的关于消费者无差异曲线的信息，对消费者的偏好描述的更充分。）,Utility Functions & Indiff. Curves,U 6,U 4,U 2,x1,x2,Utility Functions & Indiff. Curves,The collection of all indifference curves for a given preference relation is an indifference map.（给定一个偏好关系，获得所有的无差异曲线就是无差异图。） An indifference map is equivalent to a utility function; each is the other.（一个无差异图等价于一个效用函数）,Utility Functions,There is no unique utility function representation of a preference relation.（不会只有一个效用函数表示一个偏好关系。） Suppose U(x1,x2) = x1x2 represents a preference relation. Again consider the bundles (4,1), (2,3) and (2,2).,Utility Functions,U(x1,x2) = x1x2, so U(2,3) = 6 U(4,1) = U(2,2) = 4; that is, (2,3) (4,1) (2,2).,p,Utility Functions,U(x1,x2) = x1x2 (2,3) (4,1) (2,2). Define V = U2.,p,Utility Functions,U(x1,x2) = x1x2 (2,3) (4,1) (2,2). Define V = U2. Then V(x1,x2) = x12x22 and V(2,3) = 36 V(4,1) = V(2,2) = 16 so again (2,3) (4,1) (2,2). V preserves the same order as U and so represents the same preferences.,p,p,Utility Functions,U(x1,x2) = x1x2 (2,3) (4,1) (2,2). Define W = 2U + 10.,p,Utility Functions,U(x1,x2) = x1x2 (2,3) (4,1) (2,2). Define W = 2U + 10. Then W(x1,x2) = 2x1x2+10 so W(2,3) = 22 W(4,1) = W(2,2) = 18. Again, (2,3) (4,1) (2,2). W preserves the same order as U and V and so represents the same preferences.,p,p,Utility Functions: Monotonic Transformation,If U is a utility function that represents a preference relation and f is a strictly increasing function, then V = f(U) is also a utility function representing .,Goods, Bads and Neutrals,A good is a commodity unit which increases utility (gives a more preferred bundle). A bad is a commodity unit which decreases utility (gives a less preferred bundle). A neutral is a commodity unit which does not change utility (gives an equally preferred bundle).,Goods, Bads and Neutrals,Utility,Water,x,Units of water are goods,Units of water are bads,Around x units, a little extra water is a neutral.,Utility function,Some Other Utility Functions and Their Indifference Curves,Perfect substitute（完全替代） V(x1,x2) = x1 + x2. Perfect complement W(x1,x2) = minx1,x2 Quasi-linear U(x1,x2) = f(x1) + x2 Cobb-Douglas Utility Function U(x1,x2) = x1a x2b What do the indifference curves for these utility functions look like?,Perfect Substitution Indifference Curves,5,5,9,9,13,13,x1,x2,x1 + x2 = 5,x1 + x2 = 9,x1 + x2 = 13,All are linear and parallel.,V(x1,x2) = x1 + x2.,Perfect Complementarity Indifference Curves,x2,x1,45o,minx1,x2 = 8,3,5,8,3,5,8,minx1,x2 = 5,minx1,x2 = 3,All are right-angled with vertices on a ray from the origin.,W(x1,x2) = minx1,x2,Quasi-Linear Utility Functions,A utility function of the form U(x1,x2) = f(x1) + x2 is linear in just x2 and is called quasi-linear （准线性）. E.g. U(x1,x2) = 2x11/2 + x2.,Quasi-linear Indifference Curves,x2,x1,Each curve is a vertically shifted copy of the others.,Cobb-Douglas Utility Function,Any utility function of the form U(x1,x2) = x1a x2b with a 0 and b 0 is called a Cobb-Douglas utility function. E.g. U(x1,x2) = x11/2 x21/2 (a = b = 1/2) V(x1,x2) = x1 x23 (a = 1, b = 3),Cobb-Douglas Indifference Curves,x2,x1,Marginal Utilities （边际效用）,Marginal means “incremental”. （边际效用的内涵：是商品的边际增量引起的边际总效用水平。）The marginal utility of commodity i is the rate-of-change of total utility as the quantity of commodity i consumed changes; i.e.,Marginal Utilities,If U(x1,x2) = x11/2 x22 then,Marginal Utilities and Marginal Rates-of-Substitution（边际效用与边际替代率的关系）,The general equation for an indifference curve is U(x1,x2) k, a constant.（一个无差异曲线的一般函数表达式） Totally differentiating this identity gives,Marginal Utilities and Marginal Rates-of-Substitution,rearranged is,This is the MRS.,Marg. Utilities An example,Suppose U(x1,x2) = x1x2. Then,so,Marg. Utilities An example,MRS(1,8) = - 8/1 = -8 MRS(6,6) = - 6/6 = -1.,x1,x2,8,6,1,6,U = 8,U = 36,U(x1,x2) = x1x2;,Marg. Rates-of-Substitution for Quasi-linear Utility Functions,A quasi-linear utility function is of the form U(x1,x2) = f(x1) + x2.,so,Marg. Rates-of-Substitution for Quasi-linear Utility Functions,x2,x1,MRS = - f (x1) does not depend upon x2.,MRS is a constant along any line for which x1 is constant.,MRS = - f(x1),MRS = -f(x1”),x1,x1”,Monotonic Transfo