经济学的十大原理
经济学原理
N.格里高利.曼昆 著
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经济学十大原理
本章我们将探索这些问题的答案:
经济学研究什么问题?
人们如何做出决策?
人们如何相互交易?
整体经济如何运行?
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经济学十大原理
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经济学研究什么问题
稀缺性: 社会资源的有限性
经济学: 研究社会如何管理自己的稀缺资源, 比如：
人们决定购买什么, 工作多长时间，储蓄多少，
消费多少
企业决定生产多少，雇佣多少工人
社会决定如何在国防，消费物品，环境保护和其他需求之间分配资源
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经济学十大原理
经济学十大原理
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人们如何做出决策
所有决策都面临着权衡取舍。比如:
参加期中考试前一天晚上的聚会意味着更少的时间学习
想要更多的收入需要工作更长时间，这就使得休息时间减少
保护环境意味着生产消费物品的资源减少
原理一: 人们面临权衡取舍
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经济学十大原理
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人们如何做出决策
社会面临一种重要的权衡取舍: 效率 vs. 平等
效率: 社会能从其稀缺资源中得到的最大利益
平等: 经济成果在社会成员中平均分配
权衡取舍：为使社会更加平等, 需要在富人与穷人之间重新分配收入。但这会减少工作与生产的激励，并缩小经济“蛋糕”的规模
原理一: 人们面临权衡取舍
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人们如何做出决策
人们做出决策时需要比较可供选择行动方案的成本与利益
任何一种东西的机会成本是为了得到这种东西所放弃的东西
这是人们做决策的相关成本
原理二: 某种东西的成本是为了得到它所放弃的东西
经济学十大原理
经济学十大原理
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人们如何做出决策
例如：
上一年大学的机会成本不仅仅是学费，书籍，住房和伙食的钱全部加起来，还包括由于没有工作而损失的工资
看一场电影的机会成本不仅是票价，还包括你呆在剧院的时间的价值
原理二:某种东西的成本是为了得到它所放弃的东西
经济学十大原理
经济学十大原理
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人们如何做出决策
理性人：
系统而有目的地尽最大努力实现其目标的人
通过比较成本与利益的边际变动来做出决策
边际变动 – 对现有行动计划的微小增量调整
原理三: 理性人考虑边际量
经济学十大原理
经济学十大原理
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人们如何做出决策
例如:
当一个大学生考虑是否要多上一年学时，他会比较学费加上损失的工资和多上一年学所增加的额外收入
当一个经理在考虑是否要增加产出时, 她会在增加的劳动力与原材料的成本和额外的收益之间进行比较
原理三: 理性人考虑边际量
经济学十大原理
经济学十大原理
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人们如何做出决策
激励：引起一个人做出某种行为的某种东西，诸如惩罚或奖励的预期
理性人会对激励做出反应
例如：
当汽油价格上涨时, 消费者会更多的购买混合动力汽车，更少购买耗油的越野车
当烟草税上升时，青少年吸烟人数会下降
原理四: 人们会对激励做出反应
经济学十大原理
你准备出售一款1996年的野马，并且已经在这辆车的维修上面花了$1000。然而，车的变速器坏了，你能够选择再花$600将车修好，或者就此售出
在下面的情形中，你应该把变速器修好吗？并解释
A. 如果变速器正常，汽车价值是$6500 。如果不正常，则是$5700
B. 如果变速器正常，汽车价值是$6000 。如果不正常，则是$5500
主动学习 1
原理的应用
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修理变速器的成本= $600
A. 如果变速器正常，汽车价值是$6500 。如果不正常，则是$5700
修理变速器的收益= $800 ($6500 – 5700)
因此，修理变速器是值得的
B.如果变速器正常，汽车价值是$6000 。如果不正常，则是$5500
修理变速器的收益仅仅为$500
因此花费$600修理变速器是不值得的
主动学习 1
参考答案
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思考:
你最初花在维修上的 $1000没有任何影响，重要的是边际修理（变速器）的收益与成本
由A情形到B情形激励的改变导致你决策的改变
主动学习 1
参考答案
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经济学十大原理
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人们如何相互交易
人们可以专门生产一种物品或劳务并用来交换其他物品或劳务，而不必自给自足
国家之间也能从贸易与专业化中受益
将他们生产的物品出口而得到一个更好的价格
从国外进口更便宜的物品而不用在国内自己生产
原理 5 :贸易可以使每个人的状况都变得更好
经济学十大原理
经济学十大原理
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人们如何相互交易
市场: 大量的买者与卖者 (不必要在同一个地点)
组织经济活动意味着需要决定
生产什么
怎么生产
生产多少
谁将得到它们
原理 6 :市场通常是组织经济活动的一种好方法
经济学十大原理
经济学十大原理
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人们如何相互交易
市场经济：许多企业和家庭在物品和劳务市场上相互交易，通过他们的分散决策来配置资源的经济
亚当.斯密在《国富论》（1776）中的著名观察结果：
家庭和企业仿佛被一只“看不见的手”所指引，在市场上相互交易，并增进整体经济的福利
原理 6 :市场通常是组织经济活动的一种好方法
经济学十大原理
经济学十大原理
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人们如何相互交易
“看不见的手”通过价格体系来发挥作用:
买者与卖者之间的相互作用决定市场价格
每个价格即反映了物品对于买者的价值，也反映了生产物品的成本
在许多情况下，价格引导自利的家庭与企业做出使社会经济福利最大化的决策
原理 6 :市场通常是组织经济活动的一种好方法
经济学十大原理
经济学十大原理
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人们如何相互交易
政府的重要作用: 保护产权 (通过警察，法庭)
如果人们的财产存在很大的被侵犯的风险，那么他们便不愿意工作，生产，投资或者购买物品
原理 7 :政府有时可以改善市场结果
经济学十大原理
经济学十大原理
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人们如何相互交易
市场失灵：市场本身不能有效配置资源的情况
原因：
外部性：生产或消费一个物品影响到旁观者的福利（比如：污染）
市场势力：单个买者或卖者有能显著影响市场价格的能力（比如，垄断）
在这些情况下，公共政策能增进效率
原理 7 :政府有时可以改善市场结果
经济学十大原理
经济学十大原理
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人们如何相互交易
政府可以改变市场结果以促进公平
如果经济福利的市场分配结果不是合意的，税收或福利政策能改变经济“蛋糕”的分配方式
原理 7 :政府有时可以改善市场结果
经济学十大原理
政府在下述情形中发挥何种作用？政府的干预有助于结果的改善吗？
a. 公立学校
b. 工作环境安全的监管
c. 公共高速公路
d. 专利法允许制药公司对急救药索取高价
主动学习 2
问题讨论
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经济学十大原理
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整体经济如何运行
各国不同时期生活水平的巨大差异：
发达国家的平均收入是发展中国家平均收入的十倍以上
今天美国的生活水平比100年以前大约增长了八倍
原理 8 :一国的生活水平取决于它生产物品与劳务的能力
经济学十大原理
经济学十大原理
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整体经济如何运行
决定生活水平的最重要因素：生产率，即每一单位劳动投入所生产的物品与劳务数量
生产率取决于设备，劳动者的技能以及可用的技术
其它因素（比如，工会组织，国外的竞争）对于生活水平的影响远远小于生产率
原理 8 ：一国的生活水平取决于它生产物品与劳务的能力
经济学十大原理
经济学十大原理
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整体经济如何运行
通货膨胀：物价总水平的上升
长期而言，通货膨胀总是由于货币数量的过度增长而导致货币价值的下降所引起
政府创造货币的速度越快，通胀率越高
原理 9 :当政府发行了过多货币时，物价上升
经济学十大原理
经济学十大原理
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整体经济如何运行
短期内（1-2年），许多经济政策朝相反的方向推动通货膨胀与失业
其它因素使这种权衡取舍不那么明显，但这种权衡取舍一直都存在
原理 10 :社会面临通货膨胀与失业之间的短期权衡取舍
经济学十大原理
内容提要
关于个人做出决策的基本结论是：
人们面临不同目标之间的权衡取舍
任何一种行为的成本可以用其所放弃的机会来衡量
理性人通过比较边际成本与边际利益做出决策
人们根据他们所面临的激励改变自己的行为
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内容提要
关于人们之间相互交易的基本结论是：
贸易可以是互利的
市场通常是协调人们之间经济活动的一种好方法
通过纠正市场失灵或提高经济中的平等程度，政府可以潜在地改善市场结果
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内容提要
关于整体经济的基本结论：
生产率是生活水平的最终根源
货币量的增长是通货膨胀的最终根源
社会面临着通货膨胀与失业之间的短期权衡取舍
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Dear Colleague,
Thank you for using the Premium PowerPoints for Mankiw’s Principles of Economics. I update these approximately once per year, to update the data, fix any typos, and incorporate the best suggestions from users like yourself. If you have any suggestions, corrections, or feedback, please email me at rcronovich@. Check the textbook’s website to make sure you’re always using the most recent version.
In this area (the “notes” section), I occasionally include notes that are visible only to you and will not display during your presentation in class. In slides with data tables or charts, the notes area provides the source information (often a URL or web address to the original data). In other slides, the notes area provides information that might be helpful when teaching this material, particularly for new instructors and grad assistant teachers.
For chapter 1, most instructors try to cover this chapter in a single class session (especially those that are teaching the second of a two-semester sequence). If you are teaching a “principles of microeconomics” course, you might consider skipping Principles 8-10, which deal with macroeconomics.
Near the end of the chapter are four slides titled “FYI: How to Read Your Textbook.” In the notes section of these slides, I describe an in-class activity that teaches effective reading skills to students.
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You might want to elaborate a bit on some of the points made here. Some examples:
“How do people decide how much to work?” Time is scarce resource – there’s just not enough time to do everything we’d like to do. How do we decide how much of our time to spend working? There’s a tradeoff: the more time we spend working, the higher our income, and therefore the more stuff we can buy. But, the more time we spend working, the less time we have for leisure – hanging out with friends, going hiking, watching movies, etc. (You might want to ask your students how THEY decide how much time to spend working. Some will say it depends on how many classes they are taking, or the time requirements of the available jobs. But probably at least a few will say the wage – the higher the wage, the more worthwhile to work.)
“How do firms decide what kind of labor to hire?” Firms can hire unskilled or skilled workers. The skilled workers are more productive, but cost more than the unskilled workers.
“How do firms decide how much to produce?” Ask your students, and see if any of them say “it depends on the price of the product they sell.” (Probably some will say “it depends on whether there’s a lot of demand for the product”. To which you might respond “and if there’s a lot of demand for the product, what does that mean for the price that firms can get for the product?”)
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HEADS UP. The 5th edition uses “equality.” The fourth and earlier editions used “equity” here.
You may want to elaborate verbally on the last bullet to insure that the point is clear.
“Redistribute income from wealthy to poor” is accomplished through the progressive tax system, as well as social programs like food stamps and unemployment insurance that try to provide a safety net for people at the low end of the income distribution.
“But this reduces the incentive to work” – the reward for working hard is a high income. Taxes reduce this reward, and therefore reduce the incentive to work hard.
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Here’s a fun tangent if you have the class time and are so inclined:
Ask your students about the saying “The best things in life are free.” Ask them to name some of these things that supposedly are free. Ask them what “free” means in this context. The idea here is to get them to see that even things without an explicit monetary cost are not truly “free” because they have an opportunity cost.
For example, when you ask them to name the “best things” that are “free,” they will respond with answers like love, sitting at the top of a mountain you just climbed and enjoying an awesome view, or maybe witnessing the joy of a child who has just been given a new toy. In each case, there is no explicit monetary cost, but there’s an opportunity cost.
For example, a day spent climbing a mountain represents a day of foregone wages. And the fact that the mountain offers the incredible view probably means that land has been set aside for a national park that might otherwise have been used to produce industrial chemicals, or for a subdivision of million-dollar homes.
With love, it’s less obvious, but if prodded enough, your students will be able to think of non-monetary costs associated with love. For example, you might not want to see the latest Ashton Kutcher film, you might think he’s the world’s worst actor. But your boyfriend/girlfriend/teenage daughter or other loved one is DYING to see it, they are BEGGING you to take them. So you take them. That’s true love, don’t you think? And it’s certainly not free.
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See the textbook for two classic examples:
1. The diamond-water paradox: water is essential for life but virtually free; diamonds are inessential but expensive.
2. The near-zero marginal cost of an airline taking an extra passenger when the flight isn’t full.
Most of these PowerPoint chapters have two or three Active Learning activities. They break up the lecture with a short in-class activity for immediate reinforcement, application, or assessment of the material in the preceding slides.
A good idea is to give students time to formulate their answers before asking for volunteers to share their answers with the class. When the questions or exercises are more complex, consider having them work in pairs.
Digression on class participation:
In general, it’s not a good idea to try to solicit participation by saying “Now who can tell me the answer to….”. The invariable result is regular participation by very few students – the quick thinkers who have the confidence to answer spontaneously in front of the class – while most students remain silent.
When students have a bit of time to think through their answers, they are more likely to be comfortable sharing their answers with you and the class.
Even better: try a simple, time-tested activity called “THINK-PAIR-SHARE.” Pair students up. Pose a question or problem. Have students work on the problem individually for a couple minutes. Then, allow a couple minutes to work in pairs: each student tries to explain to the other why his or her answer is correct, and the other offers feedback. In many cases, they come up with better answers by working together. Finally, ask for volunteers. Students are much more likely to participate since they have had the opportunity to “test” their answers on a classmate. And those who do not participate will at least have had the chance to share their answer with, and get feedback from, one other student.
Activities like these are useful to break up a lecture every 20 minutes or so. They help maintain students’ attention spans, and increase their comprehension of the material you cover. These activities are also useful for quick, informal assessment – often, they will alert you to problems (such as students not getting what you think they’re getting) which you can then correct before moving on to cover additional material.
End of digression.
If you wish, you can omit this slide and just give this information to the class verbally.
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If each person had to grow his own food, make his own clothes, cut his own hair, we would have a world full of skinny, unfashionable poor people having bad hair days every day of the week.
It’s far more efficient for each person to specialize in producing a good or service, and then exchanging it with other people for the things they produce.
The statement “trade can make everyone better off” should not be hard to understand, if you think about it for a moment: Each of two parties would not voluntarily enter into an exchange if it made either of them worse off, now would they?
The same principles apply at the national and international level: International trade allows countries to sell their exports abroad and get a higher price, and to buy things from abroad more cheaply than they could produce at home.
In addition, trade gives a country’s consumers access to a greater variety of goods – including goods they might not be able to get at all. For example, . consumers enjoy a variety of fresh produce year-round. This would not be possible without international trade.
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A market economy is “decentralized,” meaning that there is no government committee that makes the decisions about what goods to produce and so forth. Instead, many households and firms make their own decisions:
* Each of many households decides who to work for and what goods to buy.
* Each of many firms decides whom to hire and what goods to produce.
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In all versions of this textbook except Brief Principles of Macroeconomics, market efficiency and the invisible hand are covered more thoroughly in Chapter 7.
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[“Govt” is an abbreviation for government. Throughout all of the Premium PowerPoint chapters, I try to use abbreviations the way a thoughtful instructor would use them if writing on a chalkboard. If you prefer to spell the word out, just use your mouse to highlight “govt” and then type out the full word.]
Two examples of the idea in the second bullet point:
A restaurant won’t serve meals if customers do not pay before they leave.
A music company won’t produce CDs if too many people avoid paying by making illegal copies.
Many fledging market economies are struggling through the transition from central planning because they have not developed institutions that protect and enforce property rights. The British news magazine The Economist has lots of current examples of this. An older but still interesting example comes from a column that Mankiw wrote in the June 12, 2000 issue of Fortune magazine entitled “Ukraine: How Not To Run An Economy.”
The items in this list are meant to get students thinking about Principles 6 and 7 in the context of specific examples, and to generate discussion rather than arrive at definitive answers.
NOTE: Discussing the entire list would consume a lot of class time (20-25 minutes). Two would suffice. Pick your favorite two and delete the others. Of course, you can skip this slide entirely if you wish to get through the chapter as quickly as possible.
Here are some notes which might help guide the discussion:
a. Public schools. The alternative would be private schools. The cost of education would be concentrated among those with school-aged children, rather than spread over all taxpayers, so the price per child would likely be high. Some families would not be able to afford to enroll their children in schools, and would either home-school the children or raise them without education. Is the benefit to society of having an educated population large enough to justify making people without children share in the cost? Could the private sector provide education more efficiently (either at lower cost or higher quality) than the public sector?
b. Workplace safety regulations. Without such regulations, would firms provide a safe environment for their workers? Some students will say “no – look at how bad working conditions are in poor countries which have no safety regulations.” Another view is dropping such regulations would make workers better off. Workers may view the safety of their work environment as part of their wage: the less safe the environment at a specific firm, the higher the wage the firm will have to offer to make workers willing to work there. If workers vary with respect to their tolerance for unsafe conditions, then workers with a high risk tolerance would be better off if given the option to work for higher wages in factories that aren’t as safe. Such workers would be worse off if the government required all firms to provide equally safe conditions.
c. Public highways. The alternative would be toll highways operated by the private sector. People who use highways more would pay more, and people that use them less would pay less, which seems fairer than having everyone pay equally for highways. (Actually, everyone does not pay equally - people who use public roads more buy more gas, and therefore pay more gas tax.) If there are external benefits to society of having a national highway system, then the private sector would under-provide this good.
d. Patent laws. I’ve kind of loaded the question with the wording on the slide. If you wish, change it to just “Patent laws.” Is it fair that drug companies charge such high prices for drugs that some people need to stay alive? If drug prices are regulated, how might pharmaceutical firms respond?
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“Rich countries” refers to countries like the ., Japan, and Germany.
“Poor countries” refers to countries like India, Indonesia, and Nigeria.
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While the long-run effect of increasing the quantity of money is inflation, the short-run effects are more complicated - and controversial. However, most mainstream economists believe the following: An increase in the quantity of money causes spending to rise, which causes prices to rise, which induces firms to produce more goods and services, which requires that they hire more workers. Hence, in the short-run, increasing the quantity of money causes inflation to rise, but unemployment to fall.
Of course, REDUCING the quantity of money would have the opposite effects (inflation would fall, while unemployment would rise) in the short run.
Keep in mind, though, the lesson from Principle #9: In the long run, changing the quantity of money only affects inflation. We will learn in a later chapter what determines the rate of unemployment in the long run, and we will see that it has nothing to do with the quantity of money.
The second bullet addresses the following point: In some decades, due to factors outside of the control of policymakers, inflation and unemployment are both high (. 1970s) – or low (. 1990s). Yet, given these other factors, policymakers can always reduce unemployment temporarily by creating more inflation, or vice versa.
Each Premium PowerPoint chapter ends with a summary similar to the textbook’s chapter summaries. Many instructors do not cover these chapter summaries in class.
