北大微观经济学chapter13
曼昆微观经济学chapter13
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Production function
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2
3
4
5Number of Workers Hired
Copyright © 2019 South-Western
The Production Function
● Diminishing Marginal Product
Copyright © 2006 Nelson, a division of Thomson Canada Ltd.
Total Revenue, Total Cost, and Profit
● Total Revenue
The amount a firm receives for the sale of its output.
Copyright © 2006 Nelson, a division of Thomson Canada Ltd.
The Production Function
● Diminishing Marginal Product
Diminishing marginal product is the property whereby the marginal product of an input declines as the quantity of the input increases. • Example: As more and more workers are hired at a firm, each additional worker contributes less and less to production because the firm has a limited amount of equipment.
北大微观经济学课件(英文版)ch3 Preferences
中级微观经济学
Assumptions about Preference Relations
Transitivity
(传递性): If x is at least as preferred as y, and y is at least as preferred as z, then x is at least as preferred as z; i.e.
x1
2012-10-9 中级微观经济学
Indifference Curves Exhibiting Satiation
x2
Satiation (bliss) point Better
2012-10-9
中级微观经济学
Extreme Cases of Indifference Curves; Perfect Substitutes
x2
15 I2 8 Slopes are constant at - 1.
I1
Bundles in I2 all have a total of 15 units and are strictly preferred to all bundles in I1, which have a total of only 8 units in them. x1 8 15
x
f y and y f z ~ ~
x f z.
~
2012-10-9
中级微观经济学
Indifference Curves
Take
a reference bundle x’. The set of all bundles equally preferred to x’ is the indifference curve containing x’; the set of all bundles y ~ x’. Since an indifference “curve” is not always a curve a better name might be an indifference “set”.
经济学微观经济学第十三章
经济学微观经济学第十三章在经济学的微观领域中，第十三章通常涵盖了一些重要且具有深度的概念和理论。
这一章可能会聚焦于特定的市场结构、厂商决策、消费者行为等方面。
首先，让我们来谈谈市场结构。
在微观经济学中，常见的市场结构包括完全竞争、垄断竞争、寡头垄断和完全垄断。
完全竞争市场是一种理想的市场状态，其中有众多的卖家和买家，产品同质化程度高，信息完全对称，市场参与者都是价格的接受者。
然而，在现实生活中，完全竞争市场相对较为罕见。
相比之下，垄断竞争市场则更为常见。
在这种市场中，有许多卖家提供相似但有差异的产品。
每个卖家都对自己的产品有一定的定价权，但同时也面临着来自其他竞争对手的压力。
厂商需要通过品牌建设、产品差异化等策略来吸引消费者。
寡头垄断市场则由少数几个大型企业主导。
这些企业之间的相互依存关系较为明显，它们的决策会相互影响。
例如，一家企业的价格调整可能会引发其他企业的相应反应。
完全垄断市场中，只有一个卖家控制着整个市场的供应。
这种情况可能由于法律特许权、技术专利或对关键资源的独家控制而产生。
在第十三章中，厂商的决策也是一个关键的内容。
厂商需要决定生产多少产品，以实现利润最大化。
这涉及到对成本和收益的仔细分析。
成本方面，包括固定成本（如厂房、设备等）和可变成本（如原材料、劳动力等）。
收益则取决于产品的价格和销售量。
厂商在不同的市场结构中，决策方式也有所不同。
在完全竞争市场中，由于是价格接受者，厂商只需根据市场价格来决定产量，以使边际成本等于价格。
而在垄断市场中，厂商可以通过控制产量来影响价格，从而实现利润最大化。
消费者行为也是微观经济学中的重要组成部分。
消费者在做出购买决策时，会考虑产品的价格、质量、个人偏好等因素。
消费者的需求曲线反映了在不同价格水平下消费者愿意购买的数量。
需求的变动可能受到收入、价格预期、相关商品价格等因素的影响。
此外，第十三章还可能涉及到市场失灵的相关内容。
市场并非总是能够有效地配置资源，例如存在外部性（如污染）、公共物品（如国防）、信息不对称（如二手车市场）等情况时，市场可能无法达到最优状态。
北京大学经济学院考研专业课辅导班讲义微观经济学
2012年北大经济学院考研辅导班讲义-微观目录●微观经济学部分 (3)●第一部分：消费者理论 (3)1、需求曲线与 (3)2、收入效应和替代效应 (4)3、由 (5)4、不确定条件下的选择理论 (6)●第二部分：厂商理论 (8)1、生产的三个阶段 (8)2、脊线分析 (8)3、短期与长期成本曲线 (9)4、完全竞争厂商 (9)5、完全垄断厂商 (10)6、三种价格歧视 (12)7、自然垄断 (13)8、垄断竞争厂商 (14)9、寡头厂商 (16)●第三部分：博弈论 (19)1、纳什均衡 (19)2、子博弈精炼纳什均衡（SPNE） (20)3、重复博弈 (20)●第四部分：要素市场均衡 (21)●第五部分：福利经济学 (24)1、交换的帕累托最优 (24)2、生产的帕累托最优 (24)3、生产和交换的帕累托最优 (25)4、福利经济学定理 (26)5、外部性的克服方法一：P IGOU T AX (26)6、外部性的克服方法二：制订排污标准 (27)7、外部性的克服方法三：可交易的排放许可证 (28)8、公共品 (29)●政经资本主义部分 (31)第1章商品与价值 (31)1.1商品与商品经济 (31)1.2价值、劳动价值论 (32)1.3私人劳动与社会劳动的矛盾、商品拜物教 (34)第2章货币 (34)2.1价值形式的发展与货币的起源 (34)2.2货币的职能 (35)第3章资本与剩余价值 (35)3.1资本主义与商品经济 (35)3.2资本主义生产方式的逻辑和历史基础 (35)3.3剩余价值的生产方法 (37)第4章工资、利润与地租 (38)4.1工资 (38)4.2利润 (39)4.3租金 (41)4.4地租 (42)第5章资本积累与再生产 (44)5.1单个资本的循环和周转 (44)5.2社会总资本的运行 (47)微观经济学部分●第一部分：消费者理论1、需求曲线与✧ ，和一组商品的不同价格水平相联系的均衡点的轨迹。
北京大学微观经济学 13、一般均衡和福利
一般均衡和福利PowerPoint Slides prepared by:Andreea CHIRITESCUEastern Illinois University完全竞争的价格体系•假定所有市场都是完全竞争的–经济中有大量同质的商品–每种商品都有一个均衡价格–不存在交易成本或运输成本–所有个人与厂商对于现行市场价格都完全了解一价法则•同质商品–无论谁买或无论哪一家厂商出售，同质商品的交易价格都是一样的•如果一种商品以两个不同的价格交易–需求者就会涌到价格较低的地方购买–厂商会试图在售价更为昂贵的地方进行销售•这些行动会使商品的价格趋于相同行为假设1.假定任何一种商品都有大量的买主–每个人都把所有的价格视为既定的，为了效用最大化，在他的预算约束下调整自己的行为2.假定每一种商品都有大量的厂商在生产–每个厂商都为利润最大化而经营。
在做出上述利润最大化决策时，厂商把所有的价格视为既定简单的一般均衡•假设–仅有两种商品x和y–所有个人都有相同的偏好•由无差异曲线图表示•生产可能性曲线–能被用来研究有关投入与产出的市场埃奇沃思盒状图•两种产出（x 和y ）的生产可能性曲线–k 和l 的总量是固定的•埃奇沃思盒状图–表明投入的所有可能配置–任何一点都满足全部资源在商品x 与y 之间得到完全使用图13.1 生产的埃奇沃斯盒状图的画法本图的坐标由可获得的劳动总量与资本总量给定。
用于生产x的这些资源数量从原点O x来测度；而用于生产y的数量从原点O y来测度。
盒子中的任何点都代表着把可获得的资源完全配置于两种商品生产中的情况。
是无效率的•如果把资本与劳动做些移动就可能会产出更多的x和更多的y•假设: 竞争性市场不会出现这种无效率的投入选择•我们想找到有效率的配置•两种商品的等产量线图–对于商品x的等产量线，以O x为原点–对于商品y的等产量线，以O y为原点•有效配置–出现在等产量线彼此相切的点上图13.2 生产效率的埃奇沃思盒状图本图在图13.1的基础上增加了生产x与y的产量。
2013北京大学经济学考研状元笔记-高鸿业-微观经济学
官方网址
北大、人大、中财、北外教授创办 集训营、一对一保分、视频、小班、少干、强军 第1讲 引论
微观经济学的逻辑：从亚当斯密讲起
“我们每天所需要的食物和饮料，不是出自屠户、酿酒家和面包师的恩惠，而是出于他们自利的打算。
我们不说唤起他们利他心的话，而说唤起他们利己心的话。
我们不说自己需要，而说对他们有利……” 面包师的面包好吃了，全社会福利提高了，无形的手的作用。
实质是福利经济学第一定理的表述。
第二定理是论证是否是充要条件。
当第一定理不成立时，就叫做市场失灵。
本书的章节：
第一章 引 论
第二章 需求、供给和均衡价格
第三章 效用论
第四章 生产论
第五章 成本论
第六章 完全竞争市场
第七章 不完全竞争的市场
第八章 生产要素价格的决定
第九章 一般均衡论和福利经济学
第十章 博弈论初步
第十一章 市场失灵和微观经济政策
西方经济学可以泛指大量与经济问题有关的各种不同的文献、资料和统计报告，其中包括教科书、官方文件、私营经济记录、专业或非专业著作、报刊杂志的文章和报道等等。
这些不同的文献、资料和统计报告一般说来至少应含有下列三种类别的内容。
第一，企事业经营管理方法和经验，如行情研究、存货管理、产品质量控制、车间生产流程布局等。
这类主题着重使用运筹学、数理统计和其他的方法来研究经营企事业的有效手段和总结企事业的营运经验。
2013北京大学经济学院考研状元笔记-微观经济学
对风险的态度： r ( w)
u ' ' ( w) ，如果 r(w) >0 ,风险规避者 u ' ( w)
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如果 r(w)<0，风险爱好者 如果 r(w)=0，风险中立者 确定性等价（CE）和风险升水（RP） CE：完全确定的收入水平上，该收入对于的效用水平等于风险条件下的期望效用水平 u(CE) = pu(w1) + (1—p)u(w2) 例如：u(3)=65 p=0.5 u(9)=95 那么 E(u) = 0.5 65 + 0.5 95= 80 RP = E(w) —CE 1-p=0.5
微观经济学
第一部分 消费者行为理论
需求曲线和 P.C.C 以及 I.C.C P.C.C 曲线： 其他条件不变的情况下， 一组商品在不同的价格下消费者实现最优消费的均衡点的连线的轨迹。 由 P.C.C 曲线可以推导出我们的个人消费的需求曲线。
I.C.C 曲线：其他条件不变的情况下，在不同的收入水平下消费者消费最优的均衡点的连线的轨迹。我们由 该曲线可以推导出恩格尔曲线。
TE = PQ(P)
dTE dQ P dQ Q P Q(1 ) Q(1 ed ) dP dP Q dp
如果 ed < 1，dTE/dP > 0 价格上升，TE 上升 如果 ed > 1，dTE/dP < 0 价格下降，TE 下降 TE 在图形中表示
比较斯勒茨基分析和希克斯分析
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短期和长期成本曲线 短期来说 ①TC=TVC+TFC
曼昆《经济学原理微观经济学分册》第6版课后习题详解第13章生产成本
曼昆《经济学原理（微观经济学分册）》（第6版）第5篇企业行为与产业组织第13章生产成本课后习题详解跨考网独家整理最全经济学考研真题，经济学考研课后习题解析资料库，您可以在这里查阅历年经济学考研真题，经济学考研课后习题，经济学考研参考书等内容，更有跨考考研历年辅导的经济学学哥学姐的经济学考研经验，从前辈中获得的经验对初学者来说是宝贵的财富，这或许能帮你少走弯路，躲开一些陷阱。
以下内容为跨考网独家整理，如您还需更多考研资料，可选择经济学一对一在线咨询进行咨询。
一、概念题1．总收益（total revenue）答：总收益指一定时期内厂商从一定量产品的销售中得到的货币总额，它等于单位产品的价格P乘以销售量Q，即：=⋅TR P Q由于完全竞争的厂商所面对的是一条水平的需求曲线，厂商增减一单位产品的销售所引起的总收益的变化（TR∆）总是等于固定不变的单位产品的价格P，所以总收益曲线是一条从原点出发的直线，其斜率就是固定不变的价格。
完全竞争市场外其他类型市场的总收益曲线是先上升达到最大后再下降的。
2．总成本（total cost）答：总成本指企业购买生产投入所支付的货币量，它包括两个部分，即固定成本（FC）与可变成本（VC）。
固定成本是在短期内不随产量变动而变动的生产费用，如厂房费用、机器折旧费用、一般管理费用及厂部管理人员的工资等。
只要建立了生产单位，不管产量多少，都需要支出固定成本。
可变成本是随产量变动而变动的生产费用，如原材料、燃料和动力支出及生产工人的工资等。
这些费用在短期内是随着产量的变动而变动的。
其变动的规律是：最初，在产量开始增加时，由于各种生产要素的投入比例不合理，不能充分发挥生产效率，故可变成本增加的幅度较大；以后随着产量的增加，各种生产要素的投入比例趋于合理，其效率得以充分发挥，故可变成本增加的幅度依次变小；最后由于可变要素的边际收益递减，可变成本增加的幅度依次变大。
这一变动趋势正好同边际收益递减规律所描述的总产量的变动趋势相反。
蒋殿春《高级微观经济学》课后习题详解(第13章 独占市场)
蒋殿春《高级微观经济学》第13章 独占市场跨考网独家整理最全经济学考研真题，经济学考研课后习题解析资料库，您可以在这里查阅历年经济学考研真题，经济学考研课后习题，经济学考研参考书等内容，更有跨考考研历年辅导的经济学学哥学姐的经济学考研经验，从前辈中获得的经验对初学者来说是宝贵的财富，这或许能帮你少走弯路，躲开一些陷阱。
以下内容为跨考网独家整理，如您还需更多考研资料，可选择经济学一对一在线咨询进行咨询。
1．如果一个独占厂商面对的反需求函数是10p y =-，其边际成本是常数12，求厂商的利润最大化产量。
解：根据MR MC =，有：1020.5y -=由此解出利润最大化产出为 4.75y *=。
2．市场反需求函数是100p y =，某独占厂商以两个工厂的生产来供给这个市场，成本函数分别是21112c y y =+和2222c y =。
求厂商在两个工厂的最佳产量。
解：根据两个工厂的成本函数，可得：1122c y '=+，224c y '= 当10y =，212y ≤时，()02c '=，而工厂2的边际成本不超过2，故当1y ≤时厂商将只使用工厂2，此时10y =，2y y =。
当12y >时，厂商要同时在两个工厂生产，产量分配依据边际成本相等原则，即12224y y +=，从而得到1221y y =-。
由于12y y y +=，所以有：1213y y -=，213y y += 根据需求函数，只要厂商的产量0y >，厂商总有收益100R py =≡，这是与产量无关的一个常数。
厂商要实现利润最大化，只需成本最小即可，而厂商的产量越小其成本也越小，但产量又不能为零，所以厂商只要选取一个非常小但又不为零的产量0ε>，按一开始的分析，让工厂2生产这个产量，闲置工厂1。
3．假设市场需求函数是()100a p y a -=>，独占厂商的成本函数()2c y y =。
在什么条件下厂商的产量为正？解：厂商的利润最大化问题为：()2max 10a y y y -⋅-一阶条件是：()10120a a y y ---=解得，())1151a y a +*=-⎡⎤⎣⎦。
北大微观经济学课件(英文版)Ch31 Welfare
z(2) x(3)
x(2) y(3)
2013-8-8
中级微观经济学
Aggregating Preferences
Bill x(1) y(2) z(3)
Rank-order vote results Bertha Bob (low score wins). x-score = 6 No y-score = 6 state is y(1) z(1) z-score = 6 selected!
Manipulating Preferences
Bill x(1) y(2) z(3) (4)
2013-8-8
Bertha Bob y(1) z(2) (3) x(4) z(1) (2) x(3) y(4)
中级微观经济学
These are truthful preferences. Bob introduces a new alternative and then lies. Rank-order vote results. x-score = 8 y-score = 7 z-score = 6
2013-8-8
中级微观经济学
Aggregating Preferences
Bill x(1) y(2) z(3) Bertha Bob y(1) z(2) x(3) z(1) x(2) y(3)
2013-8-8
中级微观经济学
Aggregating Preferences
Bill x(1) y(2) z(3)
Majority Vote Results x beats y
2013-8-8
中级微观经济学
Aggregating Preferences
Bill x y z Bertha Bob y z x z x y
曼昆《微观经济学》答案(英文版)_Chapter_1~5[1]
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Chapter 1Problems and Applications1. a. A family deciding whether to buy a new car faces a tradeoff between the cost of thecar and other things they might want to buy. For example, buying the car mightmean they must give up going on vacation for the next two years. So the real costof the car is the family's opportunity cost in terms of what they must give up.b. For a member of Congress deciding whether to increase spending on national parks,the tradeoff is between parks and other spending items or tax cuts. If more moneygoes into the park system, that may mean less spending on national defense or on thepolice force. Or, instead of spending more money on the park system, taxes couldbe reduced.c. When a company president decides whether to open a new factory, the decision isbased on whether the new factory will increase the firm's profits compared to otheralternatives. For example, the company could upgrade existing equipment orexpand existing factories. The bottom line is: Which method of expandingproduction will increase profit the most?d. In deciding how much to prepare for class, a professor faces a tradeoff between thevalue of improving the quality of the lecture compared to other things she could dowith her time, such as working on additional research.2. When the benefits of something are psychological, such as going on a vacation, it isn't easy tocompare benefits to costs to determine if it's worth doing. But there are two ways to think about the benefits. One is to compare the vacation with what you would do in its place. If you didn't go on vacation, would you buy something like a new set of golf clubs? Then you can decide if you'd rather have the new clubs or the vacation. A second way is to think about how much work you had to do to earn the money to pay for the vacation; then you can decide if the psychological benefits of the vacation were worth the psychological cost of working.3. If you are thinking of going skiing instead of working at your part-time job, the cost of skiingincludes its monetary and time costs, plus the opportunity cost of the wages you're giving up by not working. If the choice is between skiing and going to the library to study, then the cost of skiing is its monetary and time costs plus the cost to you of getting a lower grade in your course.4. If you spend $100 now instead of investing it for a year and earning 5 percent interest, youare giving up the opportunity to spend $105 a year from now. The idea that money has a time value is the basis for the field of finance, the subfield of economics that has to do with prices of financial instruments like stocks and bonds.5. The fact that you've already sunk $5 million isn't relevant to your decision anymore, sincethat money is gone. What matters now is the chance to earn profits at the margin. If you spend another $1 million and can generate sales of $3 million, you'll earn $2 million in marginal profit, so you should do so. You are right to think that the project has lost a total of $3 million ($6 million in costs and only $3 million in revenue) and you shouldn't have started it. That's true, but if you don't spend the additional $1 million, you won't have any sales and your losses will be $5 million. So what matters is not the total profit, but the profit you can earn at the margin. In fact, you'd pay up to $3 million to complete development; any more than that, and you won't be increasing profit at the margin.6. Harry suggests looking at whether productivity would rise or fall. Productivity is certainlyimportant, since the more productive workers are, the lower the cost per gallon of potion.Harry wants to look at average cost. But both Harry and Ron are missing the other side of the equation−revenue. A firm wants to maximize its profits, so it needs to examine both costs and revenues. Thus, Hermione is right−it’s best to examine whether the extra revenue would exceed the extra costs. In addition, Hermione is the only one who’s thinking at the margin.7. a. Since a person gets fewer after-tax Social Security benefits the greater is his or herincome, there's an incentive not to save for retirement. If you save a lot, yourincome will be higher, and you won't get as much after-tax Social Security income assomeone who didn't save as much. The unintended consequence of the taxation ofSocial Security benefits is to reduce saving; yet the Social Security system arosebecause of worries that people wouldn’t save enough for retirement.b. For the same reason, you'll tend not to work (or not work as much) after age 65.The more you work, the lower your after-tax Social Security benefits will be. Thusthe taxation of Social Security benefits discourages work effort after age 65.8. a. When welfare recipients who are able to work have their benefits cut off after twoyears, they have greater incentive to find jobs than if their benefits were to lastforever.b. The loss of benefits means that someone who can't find a job will get no income atall, so the distribution of income will become less equal. But the economy will bemore efficient, since welfare recipients have a greater incentive to find jobs. Thusthe change in the law is one that increases efficiency but reduces equity.9. By specializing in each task, you and your roommate can finish the chores more quickly. Ifyou divided each task equally, it would take you more time to cook than it would take your roommate, and it would take him more time to clean than it would take you. By specializing, you reduce the total time spent on chores.Similarly, countries can specialize and trade, making both better off. For example, suppose it takes Spanish workers less time to make clothes than French workers, and French workers can make wine more efficiently than Spanish workers. Then Spain and France can both benefit if Spanish workers produce all the clothes and French workers produce all the wine, and they exchange some wine for some clothes.10. a. Being a central planner is tough! To produce the right number of CDs by the rightartists and deliver them to the right people requires an enormous amount ofinformation. You need to know about production techniques and costs in the CDindustry. You need to know each person's musical tastes and which artists theywant to hear. If you make the wrong decisions, you'll be producing too many CDsby artists that people don't want to hear, and not enough by others.b. Your decisions about how many CDs to produce carry over to other decisions. Youhave to make the right number of CD players for people to use. If you make toomany CDs and not enough cassette tapes, people with cassette players will be stuckwith CDs they can't play. The probability of making mistakes is very high. Youwill also be faced with tough choices about the music industry compared to otherparts of the economy. If you produce more sports equipment, you'll have fewerresources for making CDs. So all decisions about the economy influence yourdecisions about CD production.11. a. Efficiency: The market failure comes from the monopoly by the cable TV firm.b. Equityc. Efficiency: An externality arises because secondhand smoke harms nonsmokers.d. Efficiency: The market failure occurs because of Standard Oil's monopoly power.e. Equityf. Efficiency: There's an externality because of accidents caused by drunk drivers.12. a. If everyone were guaranteed the best health care possible, much more of our nation'soutput would be devoted to medical care than is now the case. Would that beefficient? If you think that currently doctors form a monopoly and restrict healthcare to keep their incomes high, you might think efficiency would increase byproviding more health care. But more likely, if the government mandated increasedspending on health care, the economy would be less efficient because it would givepeople more health care than they would choose to pay for. From the point of viewof equity, if poor people are less likely to have adequate health care, providing morehealth care would represent an improvement. Each person would have a more evenslice of the economic pie, though the pie would consist of more health care and lessof other goods.b. When workers are laid off, equity considerations argue for the unemploymentbenefits system to provide them with some income until they can find new jobs.After all, no one plans to be laid off, so unemployment benefits are a form ofinsurance. But there’s an efficiency problem why work if you can get income fordoing nothing? The economy isn’t o perating efficiently if people remainunemployed for a long time, and unemployment benefits encourage unemployment.Thus, there’s a tradeoff between equity and efficiency. The more generous areunemployment benefits, the less income is lost by an unemployed person, but themore that person is encouraged to remain unemployed. So greater equity reducesefficiency.13. Since average income in the United States has roughly doubled every 35 years, we are likelyto have a better standard of living than our parents, and a much better standard of living than our grandparents. This is mainly the result of increased productivity, so that an hour of work produces more goods and services than it used to. Thus incomes have continuously risen over time, as has the standard of living.14. If Americans save more and it leads to more spending on factories, there will be an increasein production and productivity, since the same number of workers will have more equipment to work with. The benefits from higher productivity will go to both the workers, who will get paid more since they're producing more, and the factory owners, who will get a return on their investments. There's no such thing as a free lunch, though, because when people save more, they're giving up spending. They get higher incomes at the cost of buying fewer goods.15. a. If people have more money, they're probably going to spend more on goods andservices.b. If prices are sticky, and people spend more on goods and services, then output mayincrease, as producers increase output to meet the higher demand rather than raisingprices.c. If prices can adjust, then people's higher spending will be matched with increasedprices, and output won't rise.16. To make an intelligent decision about whether to reduce inflation, a policymaker would needto know what causes inflation and unemployment, as well as what determines the tradeoff between them. Because prices are sticky, an attempt to reduce inflation will lead to higher unemployment. A policymaker thus faces a tradeoff between the benefits of lower inflation compared to the cost of higher unemployment.Chapter 2Problems and Applications1. Many answers are possible.2. a. Steel is a fairly uniform commodity, though some firms produce steel of inferiorquality.b. Novels are each unique, so they are quite distinguishable.c. Wheat produced by one farmer is completely indistinguishable from wheat producedby another.d. Fast food is more distinguishable than steel or wheat, but certainly not as much asnovels.3. See Figure 2-5; the four transactions are shown.Figure 2-54. a. Figure 2-6 shows a production possibilities frontier between guns and butter. It isbowed out because when most of the economy’s resources are being used to pr oducebutter, the frontier is steep and when most of the economy’s resources are being usedto produce guns, the frontier is very flat. When the economy is producing a lot ofguns, workers and machines best suited to making butter are being used to makeguns, so each unit of guns given up yields a large increase in the production of butter;thus the production possibilities frontier is flat. When the economy is producing alot of butter, workers and machines best suited to making guns are being used tomake butter, so each unit of guns given up yields a small increase in the productionof butter; thus the production possibilities frontier is steep.b. Point A is impossible for the economy to achieve; it is outside the productionpossibilities frontier. Point B is feasible but inefficient because it’s inside theproduction possibilities frontier.Figure 2-6c. The Hawks might choose a point like H, with many guns and not much butter. TheDoves might choose a point like D, with a lot of butter and few guns.d. If both Hawks and Doves reduced their desired quantity of guns by the same amount,the Hawks would get a bigger peace dividend because the production possibilitiesfrontier is much steeper at point H than at point D. As a result, the reduction of agiven number of guns, starting at point H, leads to a much larger increase in thequantity of butter produced than when starting at point D.5. See Figure 2-7. The shape and position of the frontier depend on how costly it is to maintaina clean environment the productivity of the environmental industry. Gains inenvironmental productivity, such as the development of a no-emission auto engine, lead to shifts of the production-possibilities frontier, like the shift from PPF1 to PPF2 shown in the figure.Figure 2-76. a. A family’s decision about how much income to save is microeconomics.b. The effect of government regulations on auto emissions is microeconomics.c. The impact of higher saving on economic growth is macroeconomics.d. A f irm’s decision about how many workers to hire is microeconomics.e. The relationship between the inflation rate and changes in the quantity of money ismacroeconomics.7. a. The statement that society faces a short-run tradeoff between inflation andunemployment is a positive statement. It deals with how the economy is, not how itshould be. Since economists have examined data and found that there’s a short-runnegative relationship between inflation and unemployment, the statement is a fact,thus it’s a positive statement.b. The statement that a reduction in the rate of growth of money will reduce the rate ofinflation is a positive statement. Economists have found that money growth andinflation are very closely related. The statement thus tells how the world is, and soit is a positive statement.c. The statement that the Federal Reserve should reduce the rate of growth of money isa normative statement. It states an opinion about something that should be done,not how the world is.d. The statement that society ought to require welfare recipients to look for jobs is anormative statement. It doesn’t state a fact about how the world is. Instead, it is astatement of how the world should be and is thus a normative statement.e. The statement that lower tax rates encourage more work and more saving is apositive statement. Economists have studied the relationship between tax rates andwork, as well as the relationship between tax rates and saving. They’ve found anegative relationship in both cases. So the statement reflects how the world is, andis thus a positive statement.8. Two of the statements in Table 2-2 are clearly normative. They are: “5. If the federalbudget is to be balanced, it should be done over the business cycle rather th an yearly” and “9.The government should restructure the welfare system along the lines of a ‘negative income tax.’” Both are suggestions of changes that should be made, rather than statements of fact, so they are clearly normative statements.The other statements in the table are positive. All the statements concern how the world is, not how the world should be. Note that in all cases, even though they’re statements of fact, fewer than 100 percent of economists agree with them. You could say that positive statements are statements of fact about how the world is, but not everyone agrees about what the facts are.9. As the president, you’d be interested in both the positive and normative views of economists,but you’d probably be most interested in their positive views. Economists are on your staff to provide their expertise about how the economy works. They know many facts about the economy and the interaction of different sectors. So you’d be most likely to call on them about questions of fact posit ive analysis. Since you’re the president, you’re the one who has the make the normative statements as to what should be done, with an eye to the political consequences. The normative statements made by economists represent their views, not necessarily ei ther your’s or the electorate’s.10. There are many possible answers.11. As of this writing, the chairman of the Federal Reserve is Alan Greenspan, the chair of theCouncil of Economic Advisers is Martin N. Baily, and the secretary of the treasury is Larry Summers.12. There are many possible answers.13. As time goes on, you might expect economists to disagree less about public policy becausethey’ll have opportunities to observe different policies that are put into place. As new policies are tried, their results will become known, and they can be evaluated better. It’s likely that the disagreement about them will be reduced after they’ve been tried in practice.For example, many economists thought that wage and price controls would be a good idea for keeping inflation under control, while others thought it was a bad idea. But when the controls were tried in the early 1970s, the results were disastrous. The controls interfered with the invisible hand of the marketplace and shortages developed in many products. As a result, most economists are now convinced that wage and price controls are a bad idea for controlling inflation.But it’s unlikely that the differences between economists will ever be completely eliminated.Economists differ on too many aspects of how the world works. Plus, even as some policies get tried out and are either accepted or rejected, creative economists keep coming up with new ideas.Chapter 3Problems and Applications1. In the text example of the farmer and the rancher, the farmer’s opportunity cost of producingone pound of meat is two pounds of potatoes because for every 20 hours of work, he can produce one pound of meat or two pounds of potatoes. With limited time at his disposal, producing a pound of meat means he gives up the opportunity to produce two pounds of potatoes. Similarly, the rancher’s opportunity cost of producing one pound of meat is 1/8 pound of potatoes because for every hour of work, she can produce one pound of meat or 1/8 pound of potatoes. With limited time at her disposal, producing a pound of meat means she gives up the opportunity to produce 1/8 pound of potatoes.2. a. See Figure 3-2. If Maria spends all five hours studying economics, she can read100 pages, so that is the vertical intercept of the production possibilities frontier. Ifshe spends all five hours studying sociology, she can read 250 pages, so that is thehorizontal intercept. The time costs are constant, so the production possibilitiesfrontier is a straight line.Figure 3-2b. It takes Maria two hours to read 100 pages of sociology. In that time, she couldread 40 pages of economics. So the opportunity cost of 100 pages of sociology is40 pages of economics.3. a.Workers needed to make:One Car One Ton of GrainU.S. 1/4 1/10Japan 1/4 1/5b. See Figure 3-3. With 100 million workers and four cars per worker, if eithereconomy were devoted completely to cars, it could make 400 million cars. Since aU.S. worker can produce 10 tons of grain, if the U.S. produced only grain it wouldproduce 1,000 million tons. Since a Japanese worker can produce 5 tons of grain, ifJapan produced only grain it would produce 500 million tons. These are theintercepts of the production possibilities frontiers shown in the figure. Note thatsince the tradeoff between cars and grain is constant, the production possibilitiesfrontier is a straight line.Figure 3-3c. Since a U.S. worker produces either 4 cars or 10 tons of grain, the opportunity cost of1 car is 2½ tons of grain, which is 10 divided by 4. Since a Japanese workerproduces either 4 cars or 5 tons of grain, the opportunity cost of 1 car is1 1/4 tons of grain, which is 5 divided by 4. Similarly, the U.S. opportunity cost of1 ton of grain is 2/5 cars (4 divided by 10) and the Japanese opportunity cost of 1 tonof grain is 4/5 cars (4 divided by 5). This gives the following table:Opportunity Cost of:1 Car (in terms of tons ofgrain given up) 1 Ton of Grain (in terms ofcars given up)U.S. 2 1/2 2/5Japan 1 1/4 4/5d. Neither country has an absolute advantage in producing cars, since they’re equallyproductive (the same output per worker); the U.S. has an absolute advantage in producing grain, since it’s more productive (greater output per worker).e. Japan has a comparative advantage in producing cars, since it has a loweropportunity cost in terms of grain given up. The U.S. has a comparative advantage in producing grain, since it has a lower opportunity cost in terms of cars given up. f. With half the workers in each country producing each of the goods, the U.S. wouldproduce 200 million cars (that’s 50 million workers times 4 cars each) and 500 million tons of grain (50 million workers times 10 tons each). Japan would produce 200 million cars (50 million workers times 4 cars each) and 250 million tons of grain(50 million workers times 5 tons each).g. From any situation with no trade, in which each country is producing some cars andsome grain, suppose the U.S. changed 1 worker from producing cars to producinggrain. That worker would produce 4 fewer cars and 10 additional tons of grain.Then suppose the U.S. offers to trade 7 tons of grain to Japan for 4 cars. The U.S.will do this because it values 4 cars at 10 tons of grain, so it will be better off if thetrade goes through. Suppose Japan changes 1 worker from producing grain toproducing cars. That worker would produce 4 more cars and 5 fewer tons of grain.Japan will take the trade because it values 4 cars at 5 tons of grain, so it will be betteroff. With the trade and the change of 1 worker in both the U.S. and Japan, eachcountry gets the same amount of cars as before and both get additional tons of grain(3 for the U.S. and 2 for Japan). Thus by trading and changing their production,both countries are better off.4. a. Pat’s opportunity cost of making a pizza is 1/2 gallon of root beer, since she couldbrew 1/2 gallon in the time (2 hours) it takes her to make a pizza. Pat has anabsolute advantage in making pizza since she can make one in two hours, while ittakes Kris four hours. Kris’s opportunity cost of making a pizza is 2/3 gallons ofroot beer, since she could brew 2/3 of a gallon in the time (4 hours) it takes her tomake a pizza. Since Pa t’s opportunity cost of making pizza is less than Kris’s, Pathas a comparative advantage in making pizza.b. Since Pat has a comparative advantage in making pizza, she will make pizza andexchange it for root beer that Kris makes.c. The highest price of pizza in terms of root beer that will make both roommates betteroff is 2/3 gallons of root beer. If the price were higher than that, then Kris wouldprefer making her own pizza (at an opportunity cost of 2/3 gallons of root beer)rather than trading for pizza that Pat makes. The lowest price of pizza in terms ofroot beer that will make both roommates better off is 1/2 gallon of root beer. If theprice were lower than that, then Pat would prefer making her own root beer (she canmake 1/2 gallon of root beer instead of making a pizza) rather than trading for rootbeer that Kris makes.5. a. Since a Canadian worker can make either two cars a year or 30 bushels of wheat, theopportunity cost of a car is 15 bushels of wheat. Similarly, the opportunity cost of abushel of wheat is 1/15 of a car. The opportunity costs are the reciprocals of eachother.b. See Figure 3-4. If all 10 million workers produce two cars each, they produce atotal of 20 million cars, which is the vertical intercept of the production possibilitiesfrontier. If all 10 million workers produce 30 bushels of wheat each, they produce atotal of 300 million bushels, which is the horizontal intercept of the productionpossibilities frontier. Since the tradeoff between cars and wheat is always the same,the production possibilities frontier is a straight line.If Canada chooses to consume 10 million cars, it will need 5 million workers devotedto car production. That leaves 5 million workers to produce wheat, who willproduce a total of 150 million bushels (5 million workers times 30 bushels perworker). This is shown as point A on Figure 3-4.c. If the United States buys 10 million cars from Canada and Canada continues toconsume 10 million cars, then Canada will need to produce a total of 20 million cars.So Canada will be producing at the vertical intercept of the production possibilitiesfrontier. But if Canada gets 20 bushels of wheat per car, it will be able to consume200 million bushels of wheat, along with the 10 million cars. This is shown as pointB in the figure. Canada should accept the deal because it gets the same number ofcars and 50 million more bushes of wheat.Figure 3-46. Though the professor could do both writing and data collection faster than the student (that is,he has an absolute advantage in both), his time is limited. If the professor’s comparative advantage is in writing, it makes sense for him to pay a student to collect the data, since that’s the student’s comparative advantage.7. a. English workers have an absolute advantage over Scottish workers in producingscones, since English workers produce more scones per hour (50 vs. 40). Scottishworkers have an absolute advantage over English workers in producing sweaters,since Scottish workers produce more sweaters per hour (2 vs. 1). Comparativeadvantage runs the same way. English workers, who have an opportunity cost of1/50 sweaters per scone (1 sweater per hour divided by 50 scones per hour), have acomparative advantage in scone production over Scottish workers, who have anopportunity cost of 1/20 sweater per scone (2 sweaters per hour divided by 40 sconesper hour). Scottish workers, who have an opportunity cost of 20 scones per sweater(40 scones per hour divided by 2 sweaters per hour), have a comparative advantagein sweater production over English workers, who have an opportunity cost of 50scones per sweater (50 scones per hour divided by 1 sweater per hour).b. If England and Scotland decide to trade, Scotland will produce sweaters and tradethem for scones produced in England. A trade with a price between 20 and 50scones per sweater will benefit both countries, as they’ll be getting the traded good ata lower price than their opportunity cost of producing the good in their own country.c. Even if a Scottish worker produced just one sweater per hour, the countries wouldstill gain from trade, because Scotland would still have a comparative advantage inproducing sweaters. Its opportunity cost for sweaters would be higher than before(40 scones per sweater, instead of 20 scones per sweater before). But there are stillgains from trade since England has a higher opportunity cost (50 scones per sweater).。
北大微观经济学讲义第七章完全竞争市场
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黎诣远《微观经济学》(第3版)笔记(4.4第13章 外部性与公共品)
黎诣远《微观经济学》（第3版）第13章外部性与公共品跨考网独家整理最全经济学考研真题，经济学考研课后习题解析资料库，您可以在这里查阅历年经济学考研真题，经济学考研课后习题，经济学考研参考书等内容，更有跨考考研历年辅导的经济学学哥学姐的经济学考研经验，从前辈中获得的经验对初学者来说是宝贵的财富，这或许能帮你少走弯路，躲开一些陷阱。
以下内容为跨考网独家整理，如您还需更多考研资料，可选择经济学一对一在线咨询进行咨询。
一、外部性1．外部性的定义和分类（1）外部性的定义外部性也称外在效应或溢出效应，是指一个人或一个企业的活动对其他人或其他企业的外部影响，这种影响并不是在有关各方以价格为基础的交换中发生的，因此其影响是外在的。
（2）外部性的分类①正外部性与负外部性根据外部性的影响，可以分为正的外部性和负的外部性。
正的外部性是指一个经济主体的经济活动导致其他经济主体获得的额外经济利益，也称外部收益。
负的外部性是指一个经济主体的经济活动导致其他经济主体蒙受的额外经济损失，也称外部成本。
外部性与私人成本和社会成本、私人收益和社会收益的概念有密切关系。
私人成本和私人收益是指一种经济活动给活动者自己带来的损失和好处；社会成本和社会收益是指一种经济活动给社会带来的损失和好处。
如果一种经济活动的社会收益大于私人收益，这种经济活动就产生了正的外部性，如果一种经济活动的私人成本小于社会成本，这种经济活动就产生了负的外部性。
②生产外部性与消费外部性根据外部性产生的原因，可以分为生产的外部性和消费的外部性。
如果生产过程中存在外在成本或外在收益，生产者所承担的生产成本小于实际发生的全部社会成本，或者生产者的产品收益小于实际产生的全部社会收益，资源配置便会发生扭曲，达不到帕累托最优。
在消费过程中，当消费者给他人带来效用的增加或减少而没有为此得到补偿或付出代价时，其消费活动也具有了外部性。
③空间外部性与时间外部性根据外部性的时空结构，可以分为空间上的外部性和时间上的外部性。
新编文档-北京师范大学《微观经济学》课件-精品文档-精品文档
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经济社会面临的基本问题 1. 生产什么和生产多少? (What) 2. 如何生产? (How) 3. 为谁生产? (for Whom) 现代经济中解决上述问题的基本方式： 1. 政府统一决策 2. 市场机制调节
2. 供给表和供给曲线
第三节 供求曲线的共同作用
(均衡价格的决定与变化)
1. 均衡价格的决定 均衡价格，均衡数量，短缺，过剩
2. 均衡价格的变动 需求量的变动和需求的变动 供给量的变动和供给的变动 均衡价格的变动
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微观经济13PPT课件
© 2010 Pearson Education Canada
Monopoly and How It Arises
How Monopoly Arises A monopoly has two key features: No close substitutes Barriers to entry No Close Substitute If a good has a close substitute, even if it is produced by only one firm, that firm effectively faces competition from the producers of the substitute. A monopoly sells a good that has no close substitutes.
© 2010 Pearson Education Canada
Monopoly and How It Arises
In a natural monopoly, economies of scale are so powerful that they are still being achieved even when the entire market demand is met.
The LRAC curve is still sloping downward when it meets the demand cu
Monopoly and How It Arises
Ownership Barriers to Entry An ownership barrier to entry occurs if one firm owns a significant portion of a key resource. During the last century, De Beers owner 90 percent of the world’s diamonds.
微观经济学(第5版)第13章垄断
单一价格垄断者
Bobbie的理发店是内布拉斯加、卡罗惟一的一 家理发店。 让我们来考察卡罗的理发市场.
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管制自然垄断
平均成本定价
管制者几乎从不实行有效定价，因为由此而 来的结果是企业有利润。 相反，他们通过允许企业弥补自己所有的成 本并赚得正常利润来补偿。
管制自然垄断
平均成本定价（续）
弥补成本和正常利润的定价意味着确定的价 格等于平均总成本——称为平均成本定价规 则。 企业赚到正常利润。 这个结果是无效率的，但比无管制的利润最 大化结果要好一些。
管制自然垄断
有效的管制（续）
边际成本定价规则使受管制行业的总剩余最 大化。 边际成本定价规则是有效率的。 它使自然垄断企业有经济亏损。
管制自然垄断
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第十三章博弈论初步目前博弈论发展的非常深入，这里只是介绍一些初步知识。
在四、五十年代，由冯·诺依曼（Von Neumann）、摩根斯坦恩（Morgenstern）把对策论、运筹学引入经济学，形成了最早的博弈论。
几时年来，博弈论在经济学中发挥着越来越大的重要作用，1994年的诺贝尔经济学奖就授予三位博弈论学家：纳什（Nash）、泽尔腾（Selten）和海萨尼（Harsanyi）。
博弈论的英文是GAME THEORY，字面的意思是游戏策略，及用类似游戏中解决问题的方法，揭示解决社会、经济及其他领域问题的策略、对策，因此有的还把博弈论译成对策论。
准确的说博弈论是在给定的条件下寻求最优策略，这里给定的条件包含其他人的策略以及本人的决策对其他决策主体的影响。
策略性活动在社会、经济、政治生活中大量存在，也可以说，整个社会、经济、政治生活都是博弈行为。
因此，博弈论作为一种方法，广泛的应用在经济、政治、军事、外交中，只是博弈论在经济学中应用的最广泛、最成功。
如前面介绍过的古诺均衡、STACKELBERG均衡、CHAMBERLIN 均衡、BERTRAND 均衡、HOTELLING 均衡，都属于经济学中的博弈过程。
第一节基本概念一、博弈论1．定义：博弈论是描述、分析多人决策行为的一种决策理论，是多个经济主体在相互影响下的多元决策，决策的均衡结果取决于双方或多方的决策。
如下棋，最后的结果就是由下棋双方你来我往轮流做出决策，决策又相互影响、相互作用而得出的结果。
2．博弈论与优化理论的异同点1）相同点：博弈论与优化理论都是在给定的条件下，寻求最优决策的过程；2）不同点：A.优化理论可以看成是单人决策，而博弈理论可以看成是多人决策。
在优先理论的决策过程中，影响结果的所有变量都控制在决策者自己手里；而在博弈论的决策过程中，影响结果的变量是由多个决策者操纵的。
如企业在追求成本最小化、产量最大化、利润最大化的过程中总是假定外部条件给定，这实际上表明是一个优化问题，因为除了给定的外部条件外，剩下的因素都有决策者来控制，从而决策者自己就能控制决策的结果；如果外部条件不是给定的，而是有其他主体参与的过程，这时的决策过程就变成了一个博弈过程了，因为决策的最终结果不但取决于决策者本身，而且也取决于其他决策者的决策。
B.优化过程是一个确定的过程，而博弈过程是确定性和不确定性的统一。
优化过程是一个确定的过程，因为做出决策后，确定的结果就出来了。
说博弈过程有确定性，是因为决策各方的决策做出后，每一方的收益就确定了；说博弈过程有不确定性，在于一方做出决策后，影响结果的变量还有众多的其他决策者，在不知道其他主体行为的情况下，结果就不确定。
例如：在一次具体的战斗中，一方是否发起进攻，是一个决策。
如果发起进攻，对方肯定有所反应，客观上讲，必然会有一个确定的结果存在，这是确定性的表现。
但是最后的结果如何，取决于对方如何应对，所以在发起进攻时，并不能知道结局是怎样的，这就是不确定性的表现。
如果一方发起进攻后，另一方马上投降，则战斗结束;如果对方进行反攻，从理论上来讲，结果取决于双方实力以及双方收益的大小。
由此可以看出博弈的广泛存在，在现实生活中做出任何决策时，实际上都受到其他主体决策的影响并对我们做决策产生一定影响，决策的结果除了由我们自己决定外还要受到其他决策主体的影响，这实际上就是一个博弈过程。
二、参与者（PLAYER）参与博弈的利益主体叫做参与者。
英文原意为玩主，也有译成局中人的。
在二人博弈中，有两个参与者；在三人博弈中，有三个参与者；在多人博弈中，有多个参与者。
三、策略和策略空间：1．策略：在给定条件博弈中，参与者完整的一套行动计划叫做策略。
例如我国古代著名的谋略故事“田忌赛马”中，国王的赛马计划是：先出上等马，再出中等马，最后出下等马；田忌的赛马计划是：先出下等马，再出上等马，最后出中等马。
这里的赛马计划就是一套完整的行动计划，也就是一个策略。
2．策略空间：参与者可以选择的策略的全体就组成了策略空间。
例如在“田忌赛马”中，共有六种行动方案可供选择：上中下（先出上等马，再出中等马，最后出下等马）、上下中、中上下、中下上、下上中、下中上。
决策时田忌可以选择其中任何一个策略，在故事中，因为国王固定选择了上中下，所以田忌选择了下上中，从而赢得了比赛。
任何一人策略的改变都将使结果也随之改变，比如国王选择了中下上，而田忌选择了下上中，则国王将赢得比赛。
四、报酬函数与报酬矩阵：1．报酬函数：每一个参与博弈的参与者，他的收益依附于各个参与者所出的策略，这种收益与策略的依附关系就构成了报酬函数。
也就是说，第i个参与者的收益取决于所有参与者的策略，而不仅仅是自己的策略，表示成数学式子就是：Ri=Ri(S1，S2，。
Sn)。
其中Ri表示第i个参与者的收益，Si (i=1。
n) 表示第i个参与者所出的策略。
2．报酬矩阵：参与博弈的多个参与者的报酬可以用一个矩阵或框图表示，这样的矩阵或框图就叫做报酬矩阵。
例如有甲乙两个供货商组成一个价格卡特尔，双方都有选择遵守约定价格或者违反图 13-1矩阵中每组数字中的前一个数字表示甲的收益，后一个数字表示乙的收益。
当甲守约时，乙如果守约，收益为8，乙如果违约，收益为10；当甲违约时，乙如果守约，收益为6，乙如果违约，收益为7。
所以，当甲守约时，乙会选择违约（10>8）；当甲违约时，乙也会选择违约（7>6）。
反之不管乙如何选择，甲都会选择违约，最终的结果是双方都选择违约。
报酬:此时双方可能都选择守约，因为当甲守约时，乙会选择守约（12>10）；当甲违约时，乙也会选择守约（2>-4）。
反之不管乙如何选择，甲都会选择守约，最终的结果是双方都选择守约。
博弈过程参与者的决策行为要受到博弈规则的影响，即博弈规则的变化会改变报酬矩阵中的报酬值。
比如在图 13-1中，由于卡特尔中的每一个供货商都追求自身利益的最大化，并且没有措施来保证遵守价格约定，双方表面上可能都信誓旦旦的承诺守约，但是实际中双方会违约。
如果卡特尔追求整体利益的最大化，并且由于历史、政治、制度、惩罚等措施来保证遵守价格约定，双方就可能和平共处，遵守价格约定。
在历次中东战争中，由于民族宗教原因，OPEC石油的产量和价格都得到了严格的执行。
五、均衡及博弈的解：当博弈的所有参与者都不想改换策略时所达到的稳定状态叫做均衡，均衡的结果叫做博弈的解。
比如图13-1中甲乙两个供货商组成的卡特尔。
不管甲如何选择，乙必然选择违约，同样不论乙如何选择，甲必然选择违约。
最终双方都选择了违约，并且只要给定的条件不变，双方就都不会改变策略，结果非常稳定，达成均衡。
在这个均衡中，不管甲如何选择，乙都不会改变策略，同样无论乙如何选择，甲也不会改变策略，这种均衡就叫做占优均衡。
这种无论对方如何决策，自己总是会选择的策略叫做占优策略，由双方的占优策略所达成的均衡叫做占优均衡。
比如，在学校中，学生平时学习可能是非常努力也可能是非常懒散；老师可能把考试题出的很难，也可能出的很容易。
从博弈论的角度，这里的老师和学生就构成了一个博弈，双方的报酬矩阵如下：老师出考题学生努力学习懒散图由于老师出难题比出容易题要花费更多的时间和精力，所以收益较低，从而无论学生平时努力程度如何，老师一定选择出容易的题；由于学生只要努力学习就会取得更好的成绩，所以无论老师所出考题难度如何，学生一定会选择努力学习，这同样构成一个占优均衡。
经常遇到的还有一种均衡，是有条件的均衡叫做纳什均衡。
简单的说就是敌变我变、敌不变我亦不变。
在后面第二节中将详细介绍纳什均衡。
作业：改造图 13-3 中师生博弈的报酬函数，构造出纳什均衡。
六、囚犯两难困境：prisoners’ dilemma囚犯两难困境是博弈论中一个著名的例子，讲的是甲乙两名嫌疑犯作案后被警察抓住，分别被关在不同的屋子里受审，双方不能互通消息，每名嫌疑犯都面临坦白和不坦白两种选择。
警察告诉他们：在两人都坦白的情况下，各判刑10年；在两人都不坦白的情况下，各判刑3年；在一人坦白另一人不坦白的情况下，坦白的一方会被从轻处罚，只被判刑1年，不坦白的一方则被重判15年。
可以根据坦白后是否会受到制裁两种情况来讨论最终的均衡结果。
1.坦白后不会受到制裁时的情况：如图，在乙不坦白的情况下，如果甲坦白，甲会被从轻处罚，只被判刑1年，乙被重判15年；如果甲也不坦白，由于证据不足，甲乙都只会被判刑3年。
在乙坦白的情况下，如果甲也坦白，甲乙会被判刑10年；如果甲不坦白，乙会被从轻处罚，只被判刑1年，甲则被重判15年。
可见，在乙不坦白的情况下，甲最好是坦白，从而可以被从轻处罚；在乙坦白的情况下，因为被判刑10年总比15年要好，甲最好也是坦白，所以甲会选择坦白。
同理，无论甲如何选择，乙的最好选择也是坦白。
结果双方都选择坦白，都被判刑10年。
可见，我国公安机关“坦白从宽，抗拒从严”的心理攻势在大多数情况下都是可以奏效的。
囚犯两难困境说明个人的理性可能导致集体结果的不妙。
在现实社会中，人人都追求完美反而可能会导致社会变得很糟糕。
2.坦白后会受到制裁时的情况：博弈论的一个重要思想就是规则改变报酬矩阵，改变了报酬矩阵就会影响到行为方式。
如果犯罪组织有着严格的惩罚制度，任何一个罪犯坦白后，不论坦白的事情严重与否，犯罪组织一定会杀人灭口，并且总是能迅速做到。
这个规则将改变报酬矩阵，新的报酬矩阵如下图所示：图 13-5由于坦白后将被灭口，所以收益将是-∝。
在乙不坦白的情况下，甲最好是不坦白；在乙坦白的情况下，因为被判刑15年总比死去要好，甲最好也是不坦白，所以甲会选择不坦白。
同理，无论甲如何选择，乙的最好选择也是不坦白。
结果双方都选择不坦白，各自被判刑3年。
第二节纳什均衡一、举例假定A、B两个企业都生产白酒，白酒分为高度和低度两种。
报酬矩阵如图所示：A企业高度低度B企业高度700，600 900，1000低度800，900 600，800图 13-5A企业如果选择了生产高度白酒，那么B企业会选择生产什么呢？因为800 > 700 ，所以B企业会选择生产低度白酒。
A企业如果选择了生产低度白酒，因为900 > 600 ，那么B 企业会选择生产高度白酒。
如果B企业选择了生产高度白酒，A企业就会选择生产低度白酒。
如果B企业选择了生产低度白酒，A企业就会选择生产高度白酒。
这里，A企业的决策取决于B企业的决策，同样B企业的决策取决于A企业的决策。
但是A企业选择了生产高度白酒以后，只要不变化，B企业就会选择生产低度白酒不变化。
反过来也一样，B企业如果选择了生产高度白酒不变化，A企业就会选择生产低度白酒不变化，这实际上是一个纳什均衡，纳什均衡就是在给定别人最优的情况下，自己最优选择达成的均衡。