微观经济学需求和消费者行为PPT课件

1、需求与消费者行为,第5章,.,选择和效用理论,5.1,.,3,效用和消费者行为,Utility denotes satisfaction. More precisely, it refers to how consumers rank different goods and services. In the theory of demand, we say that people maximize their utility, which means that they choose the bundle of consumption goods (消费品束) that they most p

2、refer.,.,背景知识：边际革命,1870s前期，英国的杰文斯、侨居瑞士的法国人瓦尔拉和奥地利的门格尔，三人发起“边际革命”。,4,Lon Walras 1834-1910,Carl Menger 1840-1921,William S. Jevons 1835-1882,.,5,边际效用价值论,掀起边际革命的学者用倡导并发扬“边际效用价值论”，用主观效用价值论与当时的劳动价值论相对抗，以边际分析方法取代当时的平均分析方法，因而成为现代新古典经济学的创始人。 Marginal utility denotes the additional utility you get from the c

3、onsumption of an additional unit of a commodity,.,总效用和边际效用,6,4,3,2,1,0,.,总效用和边际效用的关系,7,Total utility,Quantity,O,U,Q,.,边际效用递减定律,随着一种物品的消费数量的增加，最后增加的物品的边际效用会不断减少。,8,Marginal utility,Quantity,O,MU,Q,.,9,序数效用,An ordinal (序数) measure simply ranks goods relative to one another. You can say you like peas b

4、etter than broccoli (花椰菜) and you like ice cream better than both of those vegetables, but you dont really need to say how much to rank your preferences (偏好) for these goods.,.,10,背景知识,用序数效用论取代基数效用论的原因有二： 对于一些不可缺少的物品的效用，基数论可能给出不合理的结果。 序数效用论比基数效用论需要的假设更少，所需的假设也更简单。,.,需求曲线的推导,5.2,.,消费者的最优化,我们假定每个消费者最大

5、化其效用，我们还假定消费者的收入是给定的，并面对给定的市场价格。 问题：当你的预算给定时，如何在不同的物品和服务中分配支出，达到的满意度最大？,12,基数效用的说明,.,13,等边际原理,Equimarginal principle: A consumer will achieve maximum satisfaction or utility when the marginal utility of the last dollar spent on a good is exactly the same as the marginal utility of the last dollar sp

6、ent on any other good. This is the utility-maximizing rule or the equimarginal principle (效用最大化准则或等边际原理).,.,等边际原理的通俗解释,如果在收入的各项支出中，从任一支出中拿出一元钱放到其他的支出中，都不会使（总）效用增加，那么原来的支出配置达到最好。,14,.,为什么需求曲线向下倾斜,The equimarginal principle perfectly explains why demand curves slope downward.,15,MU,Price,保持 不变,.,测试问题,

7、Try to fill the empty boxes correctly with either an equals sign, a greater than sign, or a less than sign.,16, =, =,consume more of good X,consume more of good Z,.,正确的回答,金钱从最后1元钱带来的效用小的地方移向效用大的地方，能够增加总效用。,17,consume more of good X,consume more of good Z,.,闲暇和最优配置,The same rule of maximum utility pe

8、r hour can be applied to many different areas of life. It is not a merely a law of economics. It is a law of rational choice (理性选择). 你是这样考虑时间安排的吗？,18,.,替代效应和收入效应,5.3,.,无差异曲线方法,Over the last few decades, economists have developed an alternative approach (方法) to analysis of demandone that makes no men

9、tion of marginal utility. This alternative approach uses “indifference curves” (无差异曲线) to rigorously and consistently (严格和一致地) produce the major propositions about consumer behavior.,20,.,21,替代效应,The first factor explaining downward-sloping demand curve is the substitution effect (替代效应). The substit

10、ution effect says that when the price of a good rises, consumers will tend to substitute other goods for the more expensive good in order to satisfy their desires more inexpensively.,.,22,收入效应,The second factor explaining downward-sloping demand curve is the income effect (收入效应). The income effect d

11、enotes the impact of a price change on a goods quantity demanded that result from the effect of the price change on consumes real incomes.,.,23,名义收入和实际收入,We have to understand the difference between nominal income (名义收入) and real income (实际收入). Nominal income is the face value of what we have in our

12、 pocket or bank account. Real income signifies the actual amount of goods and services that your income can buy.,.,从个人到市场需求,5.4,.,25,个人需求与市场需求,市场需求等于：在各个价格下，每个消费者的需求量分别相加。,.,关于市场需求的说明,由个人需求加总到市场需求，需要满足消费者之间不会相互影响的条件。 当存在个人需求随着购买物品的人数增加而增加，即人们所说的“攀比效应”时，或者存在个人需求随着购买物品的人数增加而减少，即人们所说的“虚荣效应”时，消费者互不影响的条件

13、将不满足。,26,.,27,市场供给和生产者供给,市场供给一般不能像市场需求那样，简单地将不同价格水平下各个生产者的供给量相加而得到。 原因是，各个消费者的需求之间是不能相互替代的，而各个生产者之间是相互竞争（替代）的。,.,替代品和互补品,Goods are substitutes (替代品) if an increase in the price of one increases the demand for the other. Goods are complements (互补品) if an increase in the price of one decreases the dem

14、and for the other. Goods are independent (无关的) if a price change for one has no effect on the demand for the other.,28,.,一些物品的需求价格弹性,29,.,价格弹性和替代品,The greater the number of substitutes for a good, the more elastic its demand will be. Beef has a lot of substitutes poultry (家禽), fish, and soy products

15、 (豆制品). In contrast, crack cocaine (强效可卡因) has little or no substitutes. Thats why a drug addicts (毒品上瘾者) demand is much more inelastic than a beef eaters.,30,.,31,产品定义,In this regard, the elasticity of demand also depends on how narrowly the product is defined. For example, which do you think has a

16、 more elastic demand Chevron gas or gas? 产品定义不是一件容易的事情，它涉及“量变引起质变”的分界问题，即“谷堆悖论”问题。,.,32,例子,The demand for Chevron gas is much more elastic than the demand for gas because many brands such as Shell and Texaco can be substituted for Chevron, but there is no good substitute for gas. 仍然是“同类物品越多，价格弹性越大”的

17、准则。因此，“大类”划分比“小类”划分的同类更少。,.,33,收入弹性,The income elasticity denotes the percentage change in quantity demanded divided by the percentage change in income, holding other things, such as price, constant.,.,34,一些物品的收入弹性,.,35,按收入弹性的物品分类,Normal goods (正常品) : Eis are positive. Inferior goods (劣等品) : Eis are

18、 negative. Necessities (必需品) : Eis are positive but small. Luxuries (奢侈品) : Eis are high.,.,36,毒品经济学,An addictive substance (上瘾品) is one for which the desire to consume depends significantly on past consumption. By contrast, for conventional goods, demands today are not likely to depend so directly

19、on consumption patterns (消费模式) yesterday.,.,37,(legal drugs),(illegal drugs),D,D,S,S,S,S,Quantity of addictive substance,Price of substance,Many of the negative consequences (负效应) of illegal drugs result from the prohibition of addictive substances rather than from their consumption.,重度成瘾者的需求,.,38,偶

20、尔染毒者的需求,(legal drugs),(illegal drugs),D,D,S,S,S,S,Quantity of addictive substance,Price of substance,Raising the prices of harmful addictive substances can reduce the number of casual users who will be attracted into the market.,.,塔利班禁止种鸦片,据联合国毒品控制和犯罪预防办公室统计，塔利班当政期间，阿富汗的鸦片产量下降了94%。因为阿富汗的鸦片产量占世界产量的约7

21、5%，产量下降直接反映为毒品市场生鸦片价格的变动：2000年每公斤生鸦片价值为30美元，2001年飞涨到300美元，到9月初，随着鸦片存量下降，一公斤生鸦片已经卖到700美元。 摘自“广州日报”2001年11月26日A20版,39,.,40,水与钻石悖论,Adam Smith posed the paradox (悖论，似非而是的论点) of value: Nothing is useful than water; but it will scarce purchase anything. A diamond, on the contrary, has scarce any value in

22、use; but a very great quantity of other goods may frequently be in exchange for it.,.,41,价值悖论的解释,The answer: The total utility from water consumption does not determine its price or demand. Rather, waters price is determined by its marginal utility, by the usefulness of the last glass of water. 钻石属于

23、炫耀品，不属于正常商品。,.,42,消费者剩余,The gap between the total utility of a good and its total market value is called consumer surplus (消费者剩余). Because of diminishing marginal utility, consumers satisfaction exceeds what is paid.,.,个人的消费者剩余,43,消费者实际支付,价格,均衡 价格,数量,0,需求曲线,消费者剩余,.,市场的消费者剩余,Total purchases,Consumer

24、surplus,Quantity of water,Price and marginal utility of water,Price of water,44,市场以物品的边际效用定价，称之为边际定价原则。,.,附录1,消费者均衡的几何分析 （可以选读附录2的内容）,.,46,无差异曲线,Suppose a consumer buys different combinations of two commodities, say, food and clothing, at a given set of price. If you were asked to choose between com

25、bination A and combination B, you might (1) prefer A to B, (2) prefer B to A, (3) be indifferent between A and B.,.,47,背景知识,无差异曲线方法是一种不同于基数效用论的方法，它是以序数效用论（ordinal utility theory）为基础的。 它的特点在于，你可以不知道商品对于你的效用有多大，只要能够在两个商品组合之间进行比较就可以了。,.,48,一个消费者的无差异曲线,A,B,C,D,Food,Clothing,.,49,1,C,1,0.5,替代法则,The scarc

26、er a good, the greater its relative substitution value; its marginal utility rises relative to the marginal utility of the good that has become plentiful.,3,1,1,A,B,D,Food,Clothing,.,边际替代率,50,C,F,.,无差异曲线图,51,Food,Clothing,A Family of Indifference Curves (无差异曲线簇) : Curve U4 stands for a higher level

27、of satisfaction than U3; U3 for a higher level of satisfaction than U2; and so forth.,U4,U3,U2,U1,.,52,预算线和预算约束,Food,Clothing,6,4,4,2,0,2,6,Consumers budget line (预算线): PCQC+PFQF=$6,.,53,Food,Clothing,6,4,4,2,0,2,6,C,F,.,54,切线位置的均衡,Food,Clothing,U4,U3,U2,U1,B,等边际原理：,.,55,收入变化,Food,Clothing,B,B”,.,单纯

28、价格变化,56,B,B”,A rise in the price of food makes budget line pivot (绕转) on N. The new tangency equilibrium is at B”, with less food but more or less clothing.,N,.,57,需求曲线的推导,6,4,2,0,4,2,6,PF,QF,N,.,思考问题,“Over the last few decades, economists have developed an alternative approach to analysis of demand

29、one that makes no mention of marginal utility.” 无差异曲线方法能否避开“边际效用递减定律”？,58,.,小结,效用和边际效用 等边际原理 替代效应和收入效应 替代品、互补品和独立物品 收入弹性 消费者剩余,59,.,谢谢！,60,.,附录2,参考内容,61,.,62,基数效用和序数效用,以具体的数值表示商品和劳务的效用的理论也称为基数效用理论（cardinal utility theory），这一理论有其不合理性。 经济学家也可以用序数效用理论来说明消费者的选择行为。,.,63,消费者的偏好,消费者是同时消费多种商品的，我们用“市场篮子”来表示多

30、种商品的集束。 消费者在实际中是比较不同的市场篮子的效用大小。,.,一些基本假定,假定偏好是完全的，即消费者可以比较或排列所有的市场篮子。如：在A和B中更偏好A，或更偏好B，或两者无差异。 假定偏好是可传递的，指如果消费者在A和B中更偏好A，在B和C中更偏好B，那么消费者在A和C中更偏好A。 假定所有的商品都是“好的”，指在不计成本的情况下，消费者总是偏好任何一种商品的多，而不是少。,64,.,无差异曲线,一条无差异曲线，又称等效用曲线，代表了能带给一个人相同程度满足的市场篮子的所有组合。 市场篮子A、B、D具有相同的满足程度。,65,衣服,O,40,30,20,10,10,20,30,40,

31、食物,50,50,B,A,D,.,如果商品是“好的”,市场篮子B好于市场篮子A，因为市场篮子B的商品1和商品2的数量均大于市场篮子A。,66,商品2,商品1,A,B,.,对不同市场篮子的偏好,消费者更偏好E而不是A。 消费者更偏好A而不是G或H。,67,衣服,O,40,30,20,10,10,20,30,40,食物,50,50,B,A,E,D,H,G,.,无差异曲线不能相交,假如U1与U2相交，对U1来说，市场篮子A与D等效用，对U2来说，A与B等效用。因此，市场篮子B与 D等效用。但B优于D，矛盾。,68,U1,U2,A,B,D,.,边际替代率,从A到B，用1单位食物替代3单位衣服； 从B到

32、C，需要用2单位食物替代2单位衣服； 从C到D，需要用3单位食物替代2单位衣服。,69,衣服,食物,A,B,C,D,无差异曲线,.,无差异曲线的形状,假定无差异曲线是凸的，即向内弯曲的。 无差异曲线是凸的假定，意味着一种物品的数量越来越少时要求增加越来越多的其他物品。,70,.,完全替代品,如果物品之间可以完全替代，那么无差异曲线是直线。,71,5角币,1元币,6,4,2,1,2,3,.,完全不可替代品,如果物品之间可以完全不可替代，那么无差异曲线是成直角的线。 例如，一双鞋与一双鞋加一只左脚鞋的效用一样。,72,左脚鞋,右脚鞋,3,2,1,1,2,3,.,无差异曲线簇,如果物品可以细分，那么

33、无差异曲线有无数根，构成一个无差异曲线簇（a family of indifference curves）。 越是在外面的无差异曲线，代表的偏好越大。,73,U4,U3,U2,U1,.,给定预算约束的情形,如果食物的价格为每单位 1 元，衣服的价格为每单位 2 元。给定总预算 80 元。,74,.,75,用图形描述预算约束,O,40,30,20,10,20,40,60,80,食物,衣服,.,76,预算约束和预算线,假定一个人的市场篮子由食物和衣服构成，食物的价格为PF，数量为F，衣服的价格为PC，数量为C。 如果个人的预算（收入）是有限的，比方说为I，那么它能够买的食物和衣服的组合全都在一条预算线上： PFFPCCI,.,预算线图示,设食物的价格为PF，数量为F，衣服的价格为PC，数量为C。个人的预算（收入）为I。 PFFPCCI,77,衣服,食物,.,收入变化,给定食物和衣服的价格，当收入增加时： 收入3 收入2 收入1,78,衣服,食物,收入2,收入1,收入3,.,消费者的最优选择,最优市场篮子由无差异曲线与预算线的切点确定。,79,衣服,食物,无差异曲线,最优市场篮子,预算线,.,非最优选择,如果无差异曲线与预算线相交，选择不是最优。因为B优于D，却选择了A。,80,衣服,食物,无差异曲线,预算线,A,B,D,.,最优选择的特点,从无差