1、,2 SUPPLY AND DEMAND I: HOW MARKETS WORK 供给与需求（I）：市场如何运行,The Market Forces of Supply and Demand 供给与需求的市场力量,Chapter 4,CHAPTER 4How Prices Are Determined by Market Mechanism Operation of Market Mechanism Think about forces determining Diamond vs. Food or Water,The Market Forces of Supply and Demand,Su
2、pply and demand are the two words that economists use most often. Supply and demand are the forces that make market economies work. Modern microeconomics is about supply, demand, and market equilibrium.,供给与需求的市场力量,供给和需求是经济学家最常用的两个词。 供给和需求是让市场经济运行的力量。 现代微观经济学就是关于供给、需求和市场均衡的学科。,Markets,A market is a g
3、roup of buyers and sellers of a particular good or service. The terms supply and demand refer to the behavior of people . . . as they interact with one another in markets.,市场,市场 是指某种物品或劳务的一群买者与卖者的集合。 供给与需求这两个术语是指人们在市场上相互交易时的行为。,Markets and competition 市场与竞争,Buyers determine demand. 买者决定需求,Sellers de
4、termine supply. 卖者决定供给,A Continuum of Market Structures (See 47-48 as reference),Demand Side (A)需求Quantity demanded is the amount of a good that buyers are willing and able to purchase.需求量是指买者愿意而且能够购买的一种物品或劳务的数量。,Law of Demand 需求规律,The law of demand states that there is an inverse relationship betwe
5、en price and quantity demanded.需求规律认为，价格与需求量之间的关系是负关系。,Reason of law of demand替代效应（Substitution Effect)收入效应（Income Effect） Notes on the Law of Demand Other things being equal (ceteris paribus) Exception: Giffen good and conspicuous consumption*需求法则的例外：吉芬商品和炫耀性商品,吉芬之谜与红旗车的悲剧需求定理的例外,1845年，爱尔兰发生了大灾荒，马铃
6、薯的价格上升了，需求量却增加了。这种现象与需求定理不一致，经济学家吉芬首先观察到这种现象，因此被称为“吉芬之谜”。把这种需求量与价格同向变化的低档生活必需品称为“吉芬商品”。 与吉芬之谜类似的与需求定理相反的现象还发生在高档商品身上。经济学家发现，类似高档汽车，珠宝这类高档商品，只有价格高才有人买，价格下降反而需求量减少。 我国红旗车就发生过这样的悲剧。,在20世纪80年代初，红旗车是正部级以上官员的专用车，是国产车中能代表极高身份的唯一的车型。说他是高档奢侈品不为之过。但以后，红旗车努力走普及化之路，降低价格，成为奥迪车的变种，自甘堕入普通车的行列，这时它就竞争不过其他车，走向衰落。 这两种
7、现象都违背了需求定理，请分析一下其中的原因，以及对企业决策的意义。,Demand Schedule 需求表,The demand schedule is a table that shows the relationship between the price of the good and the quantity demanded.需求表 表示一种物品的价格与需求量之间关系的表格。,Catherines Demand Schedule 凯瑟琳的需求表,Demand Curve 需求曲线,The demand curve is the downward-sloping line relati
8、ng price to quantity demanded. 需求曲线把价格与需求量联系在一起的向右下方倾斜的曲线。,Figure 1 Catherines Demand Schedule and Demand Curve,Price of,Ice-Cream Cone,0,2.50,2.00,1.50,1.00,0.50,1,2,3,4,5,6,7,8,9,10,11,Quantity of,Ice-Cream Cones,$3.00,12,图1. Catherine的需求表和需求曲线,冰激凌蛋卷 的价格,0,2.50,2.00,1.50,1.00,0.50,1,2,3,4,5,6,7,8,
9、9,10,11,冰激凌蛋卷 需求量,$3.00,12,Market Demand versus Individual Demand,Market demand refers to the sum of all individual demands for a particular good or service. Graphically, individual demand curves are summed horizontally to obtain the market demand curve.,市场需求,市场需求 是指所有个人对某种物品或劳务需求的总和。 从图形上看, 把个人需求曲线
10、水平相加，就得出了市场需求曲线。,个人需求与市场需求的关系,市场需求暗含的假设,我们根据个人需求加总得到市场需求，实际上暗含了一个假设，那就是不同消费者之间的选择行为是相互独立的。也就是说，消费者的消费行为没有相关性，不存在所谓“潮流效应”（bandwagon effect）和“自欺效应”（Snob effect）。前者是人们为追赶潮流，后者是为了标新立异而采取的在独立决策的情况下而不会发生的消费行为。,Change in Quantity Demanded versus Change in Demand,Change in Quantity Demanded Movement along t
11、he demand curve. Caused by a change in the price of the product.,需求量的变化与需求的变化,需求量的变化 沿着需求曲线移动。 是由于产品价格变动引起的。,0,D,Price of Ice-Cream Cones,Quantity of Ice-Cream Cones,A tax that raises the price of ice-cream cones results in a movement along the demand curve.,A,8,1.00,Changes in Quantity Demanded,0,D
12、,冰激凌蛋卷 的价格,冰激凌蛋卷的消费量,提高冰激凌蛋卷价格的税收引起沿着需求曲线的移动,A,8,1.00,需求量的变化,Shifts in the Demand Curve,Consumer income Prices of related goods Tastes Expectations Number of buyers,需求曲线的移动,消费者收入（京城大商场失败在哪里） 相关产品价格（EVD为什么销不出去） 偏好（唐装何以流行） 预期 （买涨不买跌与持币待购） 买者数量,Shifts in the Demand Curve,Change in Demand A shift in the
13、 demand curve, either to the left or right. Caused by a change in a determinant other than the price.,需求曲线的移动,需求的变化 需求曲线的移动，向左或者向右。 是由价格以外的因素变化引起的。,Shifts in the Demand Curve,0,D1,Price of Ice-Cream Cone,Quantity of Ice-Cream Cones,D3,D2,Increase in demand,Decrease in demand,需求曲线的移动,0,D1,冰激凌蛋卷的价格,冰激
14、凌蛋卷的数量,D3,D2,需求增加,需求减少,Consumer Income 消费者收入,As income increases the demand for a normal good will increase.收入增加，正常商品的需求增加 As income increases the demand for an inferior good will decrease.收入增加，劣等品的需求减少,Consumer Income Normal Good,$3.00,2.50,2.00,1.50,1.00,0.50,2,1,3,4,5,6,7,8,9,10,12,11,Price of Ic
15、e-Cream Cone,Quantity of Ice-Cream Cones,0,Increase in demand,An increase in income.,D1,D2,消费者收入 正常商品,$3.00,2.50,2.00,1.50,1.00,0.50,2,1,3,4,5,6,7,8,9,10,12,11,冰激凌蛋卷的价格,冰激凌蛋卷的数量,0,需求增加,收入增加.,D1,D2,Consumer Income Inferior Good,$3.00,2.50,2.00,1.50,1.00,0.50,2,1,3,4,5,6,7,8,9,10,12,11,Price of Ice-Cr
16、eam Cone,Quantity of Ice-Cream Cones,0,Decrease in demand,An increase in income.,D1,D2,消费者收入 劣等品,$3.00,2.50,2.00,1.50,1.00,0.50,2,1,3,4,5,6,7,8,9,10,12,11,冰激凌蛋卷的价格,冰激凌蛋卷的数量（返回）,0,需求减少,收入增加.,D1,D2,Prices of Related Goods Substitutes & Complements,When a fall in the price of one good reduces the deman
17、d for another good, the two goods are called substitutes. When a fall in the price of one good increases the demand for another good, the two goods are called complements.,相关物品的价格 替代品和互补品,当一种物品价格下降减少了另一种物品需求时，这两种物品被称为替代品。 当一种物品价格下降增加了另一种物品需求时，这两种物品被称为互补品。（返回）,Table 1 Variables That Influence Buyers,
18、Copyright2004 South-Western,表1. 影响买者的变量,Supply 供给,Quantity supplied is the amount of a good that sellers are willing and able to sell. 供給量是指卖者愿意而且能够出售的一种物品或劳务的数量。,Law of Supply 供给规律,The law of supply states that there is a direct (positive) relationship between price and quantity supplied. 供给规律认为，价格
19、与供給量之间的关系是正关系。,Supply Schedule 供给表,The supply schedule is a table that shows the relationship between the price of the good and the quantity supplied. 供给表是表示一种物品价格与供給量之间关系的表格。,Bens Supply Schedule 供给表,Supply Curve 供给曲线,The supply curve is the upward-sloping line relating price to quantity supplied.
20、供给曲线把价格与供給量联系在一起的向右上方倾斜的曲线。,Figure 5 Bens Supply Schedule and Supply Curve,rice of,Ice-Cream,Cone,0,2.50,2.00,1.50,1.00,1,2,3,4,5,6,7,8,9,10,11,Quantity of,Ice-Cream Cones,$3.00,12,0.50,图5. Ben供给表与供给曲线,冰激凌蛋卷 需求量,0,2.50,2.00,1.50,1.00,1,2,3,4,5,6,7,8,9,10,11,冰激凌蛋卷的供給量,$3.00,12,0.50,Market Supply vers
21、us Individual Supply,Market supply refers to the sum of all individual supplies for all sellers of a particular good or service. Graphically, individual supply curves are summed horizontally to obtain the market supply curve.,市场供给,市场供给 是指某种物品或劳务的所有卖者个人供给的总和。 从图形上看, 把个人供给曲线水平相加，就得出了市场供给曲线。,Shifts in
22、the Supply Curve,Input prices Technology Expectations Number of producers,供给曲线的移动,投入要素价格 技术 预期 生产者数量,Change in Quantity Supplied versus Change in Supply,Change in Quantity Supplied Movement along the supply curve. Caused by a change in the market price of the product.,供給量的变化与供给的变化,供給量的变化 沿着供给曲线移动。 是
23、由于产品的市场价格变动引起的。,Change in Quantity Supplied,1,5,Price of Ice-Cream Cone,Quantity of Ice-Cream Cones,0,S,1.00,A,C,A rise in the price of ice cream cones results in a movement along the supply curve.,供給量的变化,1,5,冰激凌蛋卷的价格,冰激凌蛋卷的数量,0,S,1.00,A,C,冰激凌蛋卷的市场价格上升导致供給量沿着供给曲线的移动。,Shifts in the Supply Curve,Chang
24、e in Supply A shift in the supply curve, either to the left or right. Caused by a change in a determinant other than price.,供給曲线的移动,供给的变化 供给曲线的移动，向左或者向右。 是由于价格以外的因素变化造成的。,Shifts in the Supply Curve,Price of Ice-Cream Cone,Quantity of Ice-Cream Cones,0,S1,供给曲线的移动,冰激凌蛋卷的价格,冰激凌蛋卷的数量,0,S1,Table 2 Variab
25、les That Influence Sellers,供給量的变化与供给的变化,SUPPLY AND DEMAND TOGETHER 供给与需求的结合,Equilibrium refers to a situation in which the price has reached the level where quantity supplied equals quantity demanded. 市场均衡 价格水平达到供給量与需求量相等的状态。,Supply and Demand Together,Equilibrium Price The price that balances suppl
26、y and demand. On a graph, it is the price at which the supply and demand curves intersect. Equilibrium Quantity The quantity that balances supply and demand. On a graph it is the quantity at which the supply and demand curves intersect.,供给与需求的结合,均衡价格 使供给与需求平衡的价格。 从图形上看，就是供给曲线与需求曲线相交时的价格。 均衡数量 当价格调整到
27、使供给与需求平衡时的供給量与需求量。 从图形上看，就是供给曲线与需求曲线相交时的数量。,Supply and Demand Together,Demand Schedule,Supply Schedule,At $2.00, the quantity demanded is equal to the quantity supplied!,供给与需求的结合,需求表,供给表,在 $2.00时, 需求量等于供給量!,Figure 8 The Equilibrium of Supply and Demand,Copyright2003 Southwestern/Thomson Learning,Pri
28、ce of,Ice-Cream,Cone,0,1,2,3,4,5,6,7,8,9,10,11,12,Quantity of Ice-Cream Cones,13,表8. 供给与需求的均衡,冰激凌蛋卷 需求量,0,1,2,3,4,5,6,7,8,9,10,11,12,冰激凌蛋卷的数量,13,Figure 9 Markets Not in Equilibrium,Price of,Ice-Cream,Cone,0,(a) Excess Supply,Quantity of,Ice-Cream,Cones,图9. 非均衡状态的市场,冰激凌蛋卷 需求量,0,(a) 超额供给,冰激凌蛋卷的数量,Equi
29、librium,Surplus When price equilibrium price, then quantity supplied quantity demanded. There is excess supply or a surplus. Suppliers will lower the price to increase sales, thereby moving toward equilibrium.,均衡,过剩 当价格高于均衡价格时，供給量大于需求量。 存在超额供给或过剩。 供给者通过降低价格来增加销售，这使价格向其均衡水平变动。,Equilibrium,Shortage Wh
30、en price the quantity supplied. There is excess demand or a shortage. Suppliers will raise the price due to too many buyers chasing too few goods, thereby moving toward equilibrium.,均衡,短缺 当价格低于市场均衡价格时，需求量超过了供給量。 存在着超额需求或短缺。 由于太多卖者要购买太少的物品，供给者将提高价格。因此价格将趋向于市场均衡价格。,Figure 9 Markets Not in Equilibrium,
31、Price of,Ice-Cream,Cone,0,Quantity of,Ice-Cream,Cones,(b) Excess Demand,图9. 非均衡状态的市场,冰激凌蛋卷 需求量,0,冰激凌蛋卷的数量,(b) 超额需求,Equilibrium 均衡,Law of supply and demand 需求规律 The claim that the price of any good adjusts to bring the quantity supplied and the quantity demanded for that good into balance. 认为任何一种物品价格
32、的调整都会使该物品供求平衡的观点。,Three Steps To Analyzing Changes in Equilibrium,Decide whether the event shifts the supply or demand curve (or both). Decide whether the curve(s) shift(s) to the left or to the right. Use the supply-and-demand diagram to see how the shift affects equilibrium price and quantity.,分析均
33、衡的三个步骤,确定该事件是使供给曲线移动，还是使需求曲线移动，或者使两种曲线都移动。 确定曲线是向右移动，还是向左移动。 用供求图来考察这种移动如何影响均衡价格和数量。,How an Increase in Demand Affects the Equilibrium,Price of Ice-Cream Cone,2.00,0,7,Quantity of Ice-Cream Cones,Supply,Initial equilibrium,D1,1. Hot weather increases the demand for ice cream.,需求增加如何影响均衡,冰激凌蛋卷 的价格,2.
34、00,0,7,冰激凌蛋卷的数量,供给,原来的 均衡,D1,1. 天气热使冰激凌需求增加.,Three Steps to Analyzing Changes in Equilibrium,Shifts in Curves versus Movements along Curves A shift in the supply curve is called a change in supply. A movement along a fixed supply curve is called a change in quantity supplied. A shift in the demand c
35、urve is called a change in demand. A movement along a fixed demand curve is called a change in quantity demanded.,分析均衡的三个步骤,曲线移动与沿着曲线的移动: 供给曲线的移动被称为供给的变化。 沿着固定的供给曲线的移动被称为供給量的变化。 需求曲线的移动被称为需求的变化。 沿着固定的需求曲线的移动被称为需求量的变化。,How a Decrease in Supply Affects the Equilibrium,Price of Ice-Cream Cone,2.00,0,1,
36、2,3,4,7,8,9,11,12,Quantity of Ice-Cream Cones,13,Demand,Initial equilibrium,S1,10,1. An earthquake reduces the supply of ice cream.,New equilibrium,供给减少如何影响均衡,冰激凌蛋卷 的价格,2.00,0,1,2,3,4,7,8,9,11,12,冰激凌蛋卷的数量,13,需求,原来的均衡,S1,10,地震减少了 冰激凌的供给.,新均衡,What Happens to Price and Quantity When Supply or Demand Sh
37、ifts?,当供给或需求变动时，价格和数量 会发生什么变化?,Summary,Economists use the model of supply and demand to analyze competitive markets. In a competitive market, there are many buyers and sellers, each of whom has little or no influence on the market price.,小结,经济学家用供求模型来分析竞争市场。 在竞争市场中，有许多买者和卖者，他们当中的任何一个对市场价格具有极小或者没有影响力
38、。,Summary,The demand curve shows how the quantity of a good depends upon the price. According to the law of demand, as the price of a good falls, the quantity demanded rises. Therefore, the demand curve slopes downward. In addition to price, other determinants of how much consumers want to buy inclu
39、de income, the prices of complements and substitutes, tastes, expectations, and the number of buyers. If one of these factors changes, the demand curve shifts.,小结,需求曲线表示一种物品的需求量如何取决于价格。 根据需求规律，当一种物品价格上升时，需求量减少。所以需求曲线是下倾的。 除了价格以外，决定需求量的其它因素包括收入、替代品和互补品的价格、嗜好、预期，以及买者的数量。 如果这些变量中的任何一个变化，导致需求曲线移动。,Summa
40、ry,The supply curve shows how the quantity of a good supplied depends upon the price. According to the law of supply, as the price of a good rises, the quantity supplied rises. Therefore, the supply curve slopes upward. In addition to price, other determinants of how much producers want to sell incl
41、ude input prices, technology, expectations, and the number of sellers. If one of these factors changes, the supply curve shifts.,小结,供给曲线表示一种物品的供給量如何取决于价格。 根据供给规律，当一种物品的价格上升时，供給量增加。所以供给曲线是上倾的。 除了价格以外，决定供給量的其它因素包括投入要素的价格、技术、预期，以及卖者的数量。 如果这些变量中的任何一个变化，导致供给曲线移动。,Summary,Market equilibrium is determined
42、by the intersection of the supply and demand curves. At the equilibrium price, the quantity demanded equals the quantity supplied. The behavior of buyers and sellers naturally drives markets toward their equilibrium.,小结,市场均衡是由供给曲线和需求曲线相交决定的。 在均衡价格水平上，需求量和供給量相等。 买者和卖者的行为自然地驱动 市场走向均衡。,Summary,To analy
43、ze how any event influences a market, we use the supply-and-demand diagram to examine how the even affects the equilibrium price and quantity. In market economies, prices are the signals that guide economic decisions and thereby allocate resources.,小结,为了分析一个事件如何影响市场，我们利用供求图来考察这一事件如何影响均衡价格和均衡数量。 在市场经济中，价格是指引经济决策从而配置稀缺资源的信号。,
