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“ The Economic Way of Thinking ” 12th Edition

Chapter 3 Substitutes Everywhere: The Concept of Demand. “ The Economic Way of Thinking ” 12th Edition. Chapter Outline. Introduction On the Notion of “Needs” Marginal Values Everyday Choices – Marginal Choices The Demand Curve The Law of Demand Demand and Quantity Demanded

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“ The Economic Way of Thinking ” 12th Edition

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  1. Chapter 3 Substitutes Everywhere: The Concept of Demand “The Economic Way of Thinking”12th Edition

  2. Chapter Outline • Introduction • On the Notion of “Needs” • Marginal Values • Everyday Choices – Marginal Choices • The Demand Curve • The Law of Demand • Demand and Quantity Demanded • Demand Itself Can Change • Everything Depends Upon Everything Else

  3. Chapter Outline • Misperceptions Caused by Inflation • Time Is on Our Side • Price Elasticity of Demand • Elasticity and Total Receipts • The Myth of Vertical Demand • All Scarce Goods Must Be Rationed – Somehow • Is Money All That Matters? Money Costs, Other Costs and Economic Calculation

  4. Introduction • Most goods are scarce. • Sacrifice is necessary • There are substitutes for everything • Intelligent choice entails trade-offs. • Market price signals encourage buyers to economize

  5. On the Notion of “Needs”（需要） • What is the relationship between “trade-offs” and “needs”? • Consider these four statements… • The average person needs eight glasses of water per day to maintain good health. • All citizens should be able to obtain the medical care they need regardless of their ability to pay. • A diabetic needs insulin.（糖尿病人需要胰岛素。 ） • You need to read your economics textbook.

  6. On the Notion of Needs • 这4句话均有可能产生严重的误导！ • Higher prices (sacrifices) lead people to seek substitutes （替代品）. • The fact that goods and services are scarce entails trade-offs, i.e., the sacrifice of other goods and services we value.

  7. Marginal Values • Questions • Which is more valuable, water or diamonds? • Which is more valuable, a glass of water or a glass of diamonds? • Answers • The values that matter are marginal values （。要紧的价值是边际价值）. • Marginal means “additional,”so in economics we make decisions based on expected marginal benefits versus marginal cost.

  8. Marginal Values • 经济学理论就是边际分析，因为理论假设了人们的决策是通过比较预期的额外收益和预期的额外成本做出的，收益和成本都是站在决策者所处的边界上来衡量的。 • 在经济决策当中，除了边际收益和边际成本，其他的都不重要。

  9. Everyday Choices and Marginal Choices • 通常，当我们被要求做出选择时，我们会发现，从我们的境况出发，情况往往是此多彼少或者此少彼多。 • The Economic Way of Thinking… • Rejects the all-or-nothing approach（非此即彼） • Favors attention to • Marginal benefits • Marginal costs • More of A and less of B versus more of B and less of A • （经济学的思维方式拒绝用非此即彼的方式想问题，而是注意边际收益和边际成本。）

  10. The Demand Curve • “需要”这一概念鼓励了非此即彼的思维方式，却不欣赏边际思维。 • 人们确实有需要。然而，在一个充满了稀缺性的世界里，人们要权衡利弊——少选择一点甲，是为了多选择一点乙。 • Thus, economists developed the idea of demand.

  11. The Demand Curve • 需求这个概念把人们想获得某种东西的数量与他们为了得到这些数量要付出的代价联系在一起。 • 这一概念是边际分析的深入且极其重要的应用。

  12. The Demand CurveMaking it Graphic • Graphs can be used to illustrate relationships. • Demand Curves（需求曲线） • Illustrate the relationship between price and quantity demanded. • 例如，在一个小镇上，人们的计划用水量因价格不同而不同，如表3-1所示：

  13. The Demand CurveConsumption Table 表3-1 Price per Gallon Gallons per Day $.07 23 .04 40 .02 80 .01 160 .005 320

  14. The Demand Curve • Vertical Axis – possible prices that might be charged. • Horizontal Axis – quantity purchased at those prices. • Economists call that a Demand Curve.

  15. The Demand Curve $.07 .06 .05 .04 PRICE PER GALLON .03 .02 .01 .00 0 40 80 120 160 200 240 280 320 360 400 GALLONS OF WATER PER DAY

  16. The Demand Curve • A demand curve illustrates the amount of a good that consumers plan to purchase at any given price. • Read a demand curve by taking a price and finding corresponding quantity. • That is the Quantity Demanded. • 当水价上升时，作为节约者，人们一般不会做出非此即彼的选择，而是作出边际调整。

  17. The Law of Demand • “Law of Demand”（需求法则）： • A negative relationship exists between the amount of anything that people want to purchase and the price they must pay. • 当其他条件不变时，物品价格上涨，则需求量下降；类似地，当其他条件不变时，物品价格下跌，则需求量上升。

  18. Demand and Quantity Demanded（需求和需求量） • 在使用需求概念时，必须注意，除了价格变动以外，有没有其他因素变动的可能性。最好的办法就是掌握需求和需求量的区别。 • “A change in demand” is not the same thing as a “change in quantity demanded.” • Demand is a relationship between two specific variables. • It is a schedule or a curve.

  19. P P D2 D D1 Q Q Demand and Quantity Demanded Change in Quantity demanded: Change in demand::

  20. Demand and Quantity Demanded • A change in quantity demanded is a movement from one point on a curve to another point on the same curve. • A change in demand results from some other factor that makes households buy more or less at each price. • The demand curve shifts.

  21. Demand Itself Can Change • 需求法则是说，当其他条件不变时，如果一种物品的价格变化，那么对这种物品的需求量也会随之变化。这里的关键之处在于“其他条件不变”这个短语。 • 价格对我们的选择有重要影响，但是，除了价格本身，还有其他影响因素在鼓励人们增加或是减少对商品或服务的消费。 • 需求曲线本身能移动。对某一特定物品的需求能增加也能减少。

  22. Demand Itself Can Change Price per Gallon Original Gallons/Day New Gallons/Day $.07 40 15 .04 60 25 .02 140 55 .01 240 100 .005 400 200 表 3-2

  23. Demand Itself Can Change $.07 .06 .05 .04 PRICE PER GALLON .03 .02 .01 .00 0 40 80 120 160 200 240 280 320 360 400 GALLONS OF WATER PER DAY

  24. Everything Depends Upon Everything Else • 下面我们明确分离出导致需求变动的一些影响因素，也就是能"导致需求曲线移动"的因素。 • Influences that can cause a change in demand for a good: • # of customers • Change in customer tastes • Change in income【经济学家区别正常品和低档品的唯一方法，就是看消费者对收入变化的反应如何。"低档"这一标签和质量并不存在必然联系。】

  25. Everything Depends Upon Everything Else • Change in price of a substitute【当消费者面临不同的选择时，他们也会比较其他物品的价格。其他物品的价格变化很容易引起对消费者正在考虑的物品的需求发生变化。总之，任何单个物品的价格只有在消费者将其同大量其他物品和服务的价格相比的时候才有意义。】 • Change in the price of a complementary good • Change in the expected price of a good

  26. Misperceptions Caused by Inflation • 在通货膨胀严重的时期，很多价格表面上确实上涨了，但根本不是真正的价格上涨。通货膨胀严重扭曲了我们对相对价格和成本变动的感知。 • Inflation is an increase in the average money price of goods. • If the money price of all goods (including labor) increases, then no good (except money) will have changed in real price.

  27. Misperceptions Caused by Inflation • 事实上，由于通货膨胀的作用，不是所有东西的价格都同比例地增加，这正是通货膨胀造成诸多问题的原因之一。 • 但是，各种价格还是倾向于一起变动的。所以，如果我们想要检验某一种商品价格上涨的后果，我们首先得剔除价格普遍上涨的因素。

  28. Time Is On Our Side • Changes in the quantity demanded take time. • These changes will be greater for any price change the longer the time period allowed for adjustment. • It takes time for customers to find and begin to use substitutes. • It takes time for producers to devise, produce, and publicize substitutes.

  29. Price Elasticity of Demand • Price elasticity of demand is the percentage change in the quantity demanded divided by the percentage change in price. • it measures consumer responsiveness to price changes.

  30. Price Elasticity of Demand

  31. Price Elasticity of Demand • Example • Price increases by 20% • Quantity demanded decreases by 50% • Consumers are relatively responsive - Elastic • Example • Price decreases by 20% • Quantity demanded increases by 15% • Consumers are relatively unresponsive - Inelastic

  32. Price Elasticity of Demand • Elastic Demand • Price elasticity > 1 • Inelastic Demand • Price elasticity < 1 • Unit Elastic • Price elasticity = 1

  33. Price Elasticity of Demand • …. Elasticity is influenced by: • Time • 人们对价格变化调整的时间越长，需求弹性就越大。

  34. Price Elasticity of Demand • Availability of substitutes • 消费者在面临更高的价格时，通过寻求替代品以达到节约的目的。任何东西都有替代品，但有些东西比另一些东西有更多的已知的替代品。替代品越多，需求弹性越大。替代品越少，需求弹性越小。 • 我们常常需要时间来考虑和发现适当的替代品。

  35. Price Elasticity of Demand • Proportion of one’s budget spent on a good • 预算中被用于某种东西的比例越小，消费者对价格变化的敏感度就越低。需求就越缺乏弹性。 • 如果预算中被用于某种东西的比例较大，消费者就会变得更细心，精挑细选，他们对价格变化的敏感度就越高，因此需求就更有弹性。

  36. Elasticity and Total Receipts • “The university’s total receipts from tuition would actually increase if tuition rates were cut by 20 percent.” • The 20 percent cut in prices must cause quantity demanded to increase by more than 20 percent. • Elastic demand

  37. Elasticity and Total Receipts • Elastic Demand • Prices and total receipts move in opposite directions. • Inelastic Demand • Prices and total receipts move in the same direction.

  38. P Elastic demand between C and E since OBCG < OAEF. C B E A D Q G F Elasticity and Total Receipts O

  39. P Inelastic demand between A and B. B A D Q Elasticity and Total Receipts

  40. Elasticity and Total Receipts • “It’s odd but true. Wheat farmers would gross more money if they all got together and burned one-quarter of this year’s crop.”

  41. Demand for wheat The price when 1/4 of crop is burned. The market price when entire crop is sold Elasticity and Total Receipts P Q

  42. Elasticity and Total Receipts • 不要认为大学降低了学费，同时需求又有弹性，就能得出大学总会有更好的经济状况这样的结论。没错，在需求有弹性时降低学费会使收入增加，但是入学人数的增加也同时会引起总成本的上升。在这种情况下，大学就必须决定总收入的增加是不是超过了总成本的增加。 • 一个常见的错误：很多人认为，公司为了"挣更多的钱"，需要做的全部事情就是提价。但是，一个公司如果把价格提高了20%，而需求量下降了超过20%（需求法则！），总收入就会下降。

  43. P1 D P2 The Myth of Vertical Demand P Q

  44. The Myth of Vertical Demand • Question • Does a perfectly inelastic demand curve exist? Will consumers buy the same quantity at all prices? • 在整个价格范围内，需求曲线不是完全无弹性的，没有例外。 • 完全无弹性的需求曲线是一条垂直的线，表示对某种东西来说不存在替代品。

  45. The Myth of Vertical Demand • 需求法则现在可以用弹性来表述：对整个价格范围而言，不存在完全无需求弹性的东西。 • 大多数购买者对于购买成本的变化至少会做出一点点反应，对于足够大的成本变化，所有购买者都会做出反应。 • 许多人常常谈论基本需求、最低要求、绝对必需品等等。但是需求曲线几乎从来不像他们设想的那样缺乏弹性。当然，这并不是说需求总是很有弹性的。

  46. All Scarce Goods Must Be Rationed Somehow • Market prices and willingness to pay are our primary criteria for rationing goods and services. • If a good is scarce, sacrifices must be made to obtain it. • Scarce goods must be rationed.

  47. All Scarce Goods Must Be Rationed Somehow • Rationing can be done by willingness to pay prices. • Other ways to ration: • “rationing according to need”（按需分配） • “Fist come, first served” （先到先得） • Lottery （抽签） • Equal shares for all （等分） • “Might makes right” （强权就是公理） • Merit（功绩，美德）

  48. All Scarce Goods Must Be Rationed Somehow • 这些其他分配方式每种都有其优点。但是，这些方式如果作为普遍方式来分配稀缺品，每种方式都有一些严重的缺点，在亚当·斯密所谓的"商业社会"的成员中分配尤其如此。 • 如果大多数商品都按照"先来先得"的方式进行分配，人们就要花费极多的时间用来排队。 • 抽签本身是公平的，因为没有人对稀缺品有特殊的要求权，但是完全凭偶然性来分配却忽略了人们愿望和条件的多样性。

  49. All Scarce Goods Must Be Rationed Somehow • 平均分配的困难在于，有时候某种东西很难被分割得很均匀，有时候每一份的价值太低，以至于对人没有意义。 • “强权就是公理”的原则有明显的缺陷，不光是对弱者，对强者也是一样，人们被迫花费宝贵的资源来捍卫自己的那一份。 • 按照功绩分配不失为一个明智的方式，但是，前提条件是人们对什么是功绩以及用什么程序来决定某人拥有什么功绩要有一致的认识；而这些条件在很小的社会圈子（比如密切结合的家庭）之外几乎无法满足。

  50. All Scarce Goods Must Be Rationed Somehow • 最重要的是，上面讨论的这些其他分配原则都没有考虑供给的问题。很少有什么东西是从天而降，所能供给的数量很少是与分配方式无关的。 • 大多数商品都是人生产的，而人们都想让他们的努力得到回报。如果一种稀缺品的分配方式不能使生产这些商品的人们得到适当的回报，那么这种分配方式最终一定会崩溃。

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