1、The Market Forces of Supply and Demand 供给与需求的市场力量,Chapter 4,The Market Forces of Supply and Demand,Supply and Demand are the two words that economists use most often. 供给和需求是经济学家最常用的两个术语。 Supply and Demand are the forces that make market economies work. 供给和需求即是推动市场经济运行的力量所在 Modern microeconomics is a
2、bout supply, demand and equilibrium. 现代微观经济学研究供给、需求和均衡。,Markets市场,A market is a group of buyers and sellers of a particular good or service.市场是由某个商品或服务的买者和买者组成的群体 The terms supply and demand refer to the behavior of people as they interact with one another in markets.术语供给和需求指人们的行为当他们在市场中相互作用时。 The b
3、uyers as a group determine the demand. 买方作为一个整体决定需求 The sellers as a group determine the supply. 卖方作为一个整体决定供给,Market Type 市场类型,A competitive market is a market in which竞争性市场是指这样的市场： with many buyers and many sellers 有许多的买者和卖者 that is not controlled by any one person 市场不受任何一个人操纵 in which a narrow ran
4、ge of prices are established that buyers and sellers act upon. 买者和卖者所遵循的价格被约束在窄小的范围内。,Competition: Perfect and otherwise 竞争：完全竞争与否,Perfect competition:完全竞争 Products are all the same 产品完全相同 Numerous buyers and sellers so that each has no influence over the price 有无数的卖者和买者以至与任何人不能影响价格 Buyers and selle
5、rs are price takers 买者和买者都是价格接受者 No entry barriers 没有进入壁垒,Competition: Perfect and otherwise 竞争：完全竞争与否,Monopoly:完全垄断 One seller, seller controls price一个卖者，买者控制价格 Oligopoly:寡头垄断 Few sellers少数几个卖者 Not always aggressive competition竞争不一定总是很激烈。 Monopolistic Competition:垄断竞争 Many sellers许多卖者 Slightly diff
6、erentiated products产品有微小差别 Each seller may set price for its own product每一个卖者都能为自己的产品设定价格。,Demand需求,Quantity demanded is the amount of a good that buyers are willing and able to purchase. 需求量是买者愿意且能够购买的量 The Law of Demand states that, ceteris paribus, there is an inverse relationship between price a
7、nd quantity demanded (Giffen Goods ). 需求法则是说，其他条件不变的情况下，价格和需求量负相关（吉芬商品） Ceteris paribus is a Latin phrase that means all variables other than the ones being studied are assumed to be constant. Literally, it means other things being equal. Ceteris Paribus是一个拉丁习词，指除了被研究的变量外，其他变量都假定是不变的。,Demand Schedul
8、e and Curve,$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-Cream Cone,Quantity of Ice-Cream Cones,0,Market Demand市场需求,Marker demand refers to the sum of all individual demands for a particular good or service. 市场需求是所有个人对某个商品或服务的需求总和。 Graphically, individual demand curves are
9、summed horizontally to obtain the market demand curve. 从图形上看，将个人需求曲线水平加总就得到了市场需求曲线。,The Market Demand Curve,Price of Ice-Cream Cone,Price of Ice-Cream Cone,Price of Ice-Cream Cone,2.00,2.00,2.00,4,3,7,1.00,1.00,1.00,8,5,13,Quantity of Ice-Cream Cones,Quantity of Ice-Cream Cones,Quantity of Ice-Cream
10、 Cones,Catherines Demand,Nicholass Demand,Market Demand,+,=,When the price is $2.00, Catherine will demand 4 ice-cream cones.,When the price is $2.00, Nicholas will demand 3 ice-cream cones.,The market demand at $2.00 will be 7 ice-cream cones.,When the price is $1.00, Catherine will demand 8 ice-cr
11、eam cones.,When the price is $1.00, Nicholas will demand 5 ice-cream cones.,The market demand at $1.00, will be 13 ice-cream cones.,The market demand curve is the horizontal sum of the individual demand curves!,Determinants of Demand 需求的决定因素,Marker price市场价格 Consumer income消费者收入 Prices of related go
12、ods相关商品的价格 Tastes偏好 Expectations预期 Population人口,Change in Quantity Demanded vs. Change in Demand,Change in Quantity Demanded需求量的变化 Movement along the demand curve.沿着需求曲线 Caused by a change in the price of the product.由商品价格变化导致 Change in Demand需求的变化 A shift in the demand curve, either to the left or
13、right.需求曲线发生移动：左移或右移 Caused by a change in a determinant other than the price.由除了价格以外的影响需求的其他因素变化导致,Changes in Quantity Demanded,0,D1,Price of Cigarettes per Pack,Number of Cigarettes Smoked per Day,A tax that raises the price of cigarettes results in a movement along the demand curve.,A,20,2.00,Cha
14、nges in Demand,0,D1,Price of Ice-Cream Cone,Quantity of Ice-Cream Cones,D3,D2,Increase in demand,Decrease in demand,Consumer Income,As income increases the demand for a normal good will increase. 随着收入的增加，对正常品的需求会增加 Necessaries必需品 Luxuries奢侈品 As income increases the demand for an inferior good will d
15、ecrease. 随着收入的增加，对劣等品的需求会减少,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 Ice-Cream Cone,Quantity of Ice-Cream Cones,0,Increase in demand,An increase in income.,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
16、,11,Price of Ice-Cream Cone,Quantity of Ice-Cream Cones,0,Decrease in demand,An increase in income.,D1,D2,Prices of Related Goods Substitutes & Complements,When a fall in the price of one good reduces the demand for another good, the two goods are called substitutes. 如果一个商品的价格下降会减少另外一个商品的需求，则这两种商品称为
17、替代品。 When a fall in the price of one good increases the demand for another good, the two goods are called complements. 如果一个商品的价格下降会增加另外一个商品的需求，则这两种商品称为互补品。,Change in Quantity Demanded versus Change in Demand,Variables that Affect Quantity Demanded,A Change in This Variable . . .,Price,Represents a m
18、ovement,along the demand curve,Income,Shifts the demand curve,Prices of related,goods,Shifts the demand curve,Tastes,Shifts the demand curve,Expectations,Shifts the demand curve,Number of,buyers,Shifts the demand curve,Supply供给,Quantity supplied is the amount of a good that sellers are willing and a
19、ble to sell. 供给量是指一个商品的销售者愿意且能够销售的数量。 The Law of Supply states that there is a positive relationship between price and quantity supplied. (land, relics, superstar) 供给法则是指价格和供给量正相关（土地、遗迹、超级明星）,Supply Curve,$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-Cream Cone,Quantity of I
20、ce-Cream Cones,0,Market Supply市场供给,Market supply refers to the sum of all individual supplies for all sellers of a particular good or service. 市场供给曲线是指某个商品或服务所有的卖者的供给量之和 Graphically, individual supply curves are summed horizontally to obtain the market supply curve. 从图像上看，将个人供给水平加总就可得到市场供给。,Determin
21、ants of Supply 供给的决定因素,Market price市场价格 Inputs prices投入品价格 Technology技术 Expectations期望 Number of producers生产者的数量,Change in Quantity Supplied versus Change in Supply,Change in Quantity Supplied供给量的变化 Movement along the supply curve.沿着供给曲线 Caused by a change in the market price of the product.由产品的市场价格
22、变化导致 Change in Supply供给的变化 A shift in the supply curve, either to the left or right. 供给曲线移动：左移或右移 Caused by a change in a determinant other than price. 由除价格以外的供给影响因素变化导致,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
23、cones results in a movement along the supply curve.,Change in Supply,Price of Ice-Cream Cone,Quantity of Ice-Cream Cones,0,S1,Change in Quantity Supplied versus Change in Supply,Supply and Demand Together,Equilibrium均衡 A situation in which quantity supplied equals quantity demanded.供给量等于需求量的状态 Equil
24、ibrium Price均衡价格 The price that balances supply and demand. 使得供给和需求均衡时的价格 Equilibrium Quantity均衡数量 The quantity that balances supply and demand. 使得供给和需求相等时的数量,Price of Ice-Cream Cone,Quantity of Ice-Cream Cones,Equilibrium of Supply and Demand,2,1,3,4,5,6,7,8,9,10,12,11,0,$3.00,2.50,2.00,1.50,1.00,0
25、.50,Price of Ice-Cream Cone,Quantity of Ice-Cream Cones,2,1,3,4,5,6,7,8,9,10,12,11,0,$3.00,2.50,2.00,1.50,1.00,0.50,Supply,Demand,Surplus,Excess Supply,Excess Demand,Quantity of Ice-Cream Cones,Price of Ice-Cream Cone,$2.00,0,1,2,3,4,5,6,7,8,9,10,11,12,13,Supply,Demand,$1.50,Shortage,Three Steps to
26、Analyze Changes in Equilibrium,Decide whether the event shifts the supply or demand curve (or both). 确定事件是移动供给曲线还是需求曲线（或两者） Decide whether the curve(s) shift(s) to the left or to the right. 确定曲线是左移还是右移 Examine how the shift affects equilibrium price and quantity. 确定曲线的移动如何影响均衡价格和数量,How an Increase i
27、n 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.,How a Decrease in Supply Affects the Equilibrium,Price of Ice-Cream Cone,2.00,0,1,2,3,4,7,8,9,11,12,Quantity of Ice-Cream Con
28、es,13,Demand,Initial equilibrium,S1,10,1. An earthquake reduces the supply of ice cream.,New equilibrium,Summary,Economists use the model of supply and demand to analyze competitive markets. 经济学家使用供给需求模型来分析竞争性市场 The demand curve shows how the quantity of a good depends upon the price. 需求曲线表明需求量如何依赖于
29、价格 According to the law of demand, as the price of a good rises, the quantity demanded falls. 根据需求法则，价格上升会导致需求量下降 In addition to price, other determinants of quantity demanded include income, tastes, expectations, and the prices of complements and substitutes.,Summary,The supply curve shows how the
30、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. In addition to price, other determinants of quantity supplied include input prices, technology, and expectations. Market equilibrium is determined by the intersection of the supply and demand curves.,Summary,Supply and demand together determine the prices of the economys goods and services. In market economies, prices are the signals that guide the allocation of resources. Please refer to the textbook: How prices allocate resources.,
