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 4Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.The Market Forces of Supply and DemanduSupply and demand are the two words that economists use most often.uSupply and demand are the forces that make market economies work.uModern microeconomics is about supply, demand, and market equilibrium.Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.供给与需求的市场力量n供给和需求是经济学家最常用的 两个词。n供给和需求是让市场经济运行的 力量。n现代微观经济学就是关于供给、 需求和市场均衡的学科。Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.Markets uA market is a group of buyers and sellers of a particular good or service. uThe terms supply and demand refer to the behavior of people . . . as they interact with one another in markets. Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.市场 u市场 是指某种物品或劳务的一群买者与卖者的集合。 u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。Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.Markets and competition市场与竞争u Buyers determine demand. 买者决定需求u Sellers determine supply. 卖者决定供给Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.A Competitive Market 竞争市场A competitive market is a market in which there are many buyers and sellers so that each has a negligible impact on the market price竞争市场有很多买者和卖者的 市场，所以每一个买者或卖者对市 场价格的影响都可以忽略不计。Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.Competition: Perfect and OtherwiseuProducts are the sameuNumerous buyers and sellers so that each has no influence over priceuBuyers and Sellers are price takersPerfect CompetitionHarcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.竞争: 完全及其它u产品是完全相同的。u买者和卖者如此之多，以至于没有 一个买者或卖者可以影响价格。u买者和卖者都是价格接受者。完全竞争Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.Competition: Perfect and OtherwiseuMonopolyuOne seller, and seller controls priceuOligopolyuFew sellersuNot always aggressive competitionHarcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.竞争: 完全及其它u垄断u一个卖者，卖者决定价格。u寡头u少数几个卖者。u并不总是主动地进行竞争。Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.Competition: Perfect and OtherwiseuMonopolistic CompetitionuMany sellersuSlightly differentiated productsuEach seller may set price for its own productHarcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.竞争: 完全及其它u垄断竞争u许多卖者u略有差异的产品u每个卖者都有决定自己产品价格 的能力Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.Demand 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。Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.Law of Demand 需求规律The law of demand states that there is an inverse relationship between 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。Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.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。Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.Catherines Demand Schedule 凯瑟琳的需求表Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.Demand Curve 需求曲线The demand curve is the downward- sloping line relating 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 Scheduleand Demand CurvePrice of Ice-Cream Cone02.502.001.501.000.50123456789 10 11Quantity of Ice-Cream Cones$3.00121. A decrease in price .2. . increases quantity of cones demanded.图1. Catherine的需求表和需求曲线冰激凌蛋卷 的价格02.502.001.501.000.50123456789 10 11 冰激凌蛋卷 需求量$3.00121. 价格下降2. . 蛋卷的需求量上升。Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.Market Demand versus Individual DemanduMarket demand refers to the sum of all individual demands for a particular good or service.uGraphically, individual demand curves are summed horizontally to obtain the market demand curve.Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.市场需求u市场需求 是指所有个人对某种物 品或劳务需求的总和。u从图形上看, 把个人需求曲线水平 相加，就得出了市场需求曲线。Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.Change in Quantity Demanded versus Change in DemandChange in Quantity DemandeduMovement along the demand curve.uCaused by a change in the price of the product.Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.需求量的变化与需求的变化需求量的变化u沿着需求曲线移动。u是由于产品价格变动引起的。Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.0DPrice of Ice- Cream ConesQuantity of Ice-Cream ConesA tax that raises the price of ice-cream cones results in a movement along the demand curve.AB81.00$2.004Changes in Quantity DemandedHarcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.0D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AB81.00$2.004需求量的变化H