需求供給與市場價格

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第二章供給與需求（ I）：市場如何運行SUPPLY AND DEMAND I: HOW MARKETS WORK n “ 你可以使一只鸚鵡成為經(jīng) 濟學(xué) 家，但前提必須是讓它明白供給和需求 ”n -薩繆爾遜經(jīng) 濟學(xué) 思考：n 1、農(nóng) 業(yè) 的好消息是否是農(nóng) 民的好消息？n 2、最低工資法是否是保障工人福利的好制度？ 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. 供給與需求的市場力量n 供給和需求是經(jīng) 濟學(xué) 家最常用的兩個詞。

（ Supply and demand are the two words that economists use most often ）n 供給和需求是讓市場經(jīng) 濟運行的力量 n （ Supply and demand are the forces that make market economies work.）n （ Modern microeconomics is about supply, demand, and market equilibrium. ）現(xiàn) 代微觀經(jīng) 濟學(xué) 就是關(guān) 于供給、需求和市場均衡的學(xué) 科 MarketsuA market is a group of buyers and sellers of a particular good or service. 市場u市場是指某種物品或勞務(wù) 的一群買者與賣者的集合 Markets and competition 市場與競爭u Buyers determine demand. 買者決定需求u Sellers determine supply. 賣者決定供給 A Competitive Market 完全競爭市場 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 競爭市場有很多買者和賣者的市場，所以每一個買者或賣者對市場價格的影響都可以忽略不計。

Competitive Market完全競爭市場uProducts are the sameuNumerous buyers and sellers so that each has no influence over priceuBuyers and Sellers are price takers產(chǎn) 品是完全相同的買者和賣者如此之多，以至于沒有一個買者或賣者可以影響價格買者和賣者都是價格接受者 Competition: Perfect and Otherwiseu Monopolyu One seller, and seller controls priceu Oligopolyu Few sellersu Not always aggressive competitionu壟斷u一個賣者，賣者決定價格 u寡頭 u少數(shù) 幾個賣者 u并不總是主動地進(jìn) 行競爭 Competition: Perfect and OtherwiseuMonopolistic CompetitionuMany sellersuSlightly differentiated productsuEach seller may set price for its own product 競爭 : 完全及其它u壟斷競爭u許多賣者u略有差異的產(chǎn) 品u每個賣者都有決定自己產(chǎn) 品價格的能力 Demand 需求Quantity demanded is the amount of a good that buyers are willing and able to purchase. 需求量是指買者愿意而且能夠購買的一種物品或勞務(wù) 的數(shù) 量。

Law of Demand 需求規(guī) 律The law of demand states that there is an inverse relationship between price and quantity demanded. 需求規(guī) 律認(rèn) 為，價格與需求量之間的關(guān) 系是負(fù) 關(guān) 系 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. 需求表表示一種物品的價格與需求量之間關(guān) 系的表格 Catherines Demand Schedule 凱瑟琳的需求表Price 價格 Quantity 數(shù) 量 $0.00 12 0.50 10 1.00 8 1.50 6 2.00 4 2.50 2 3.00 0 Demand Curve 需求曲線The demand curve is the downward-sloping line relating price to quantity demanded. 需求曲線把價格與需求量聯(lián) 系在一起的向右下方傾斜的曲線。

Figure 1 Catherines Demand Schedule and Demand Curve （ Catherines的需求表和需求曲線）Price ofIce-Cream Cone冰激凌蛋卷的價格 02.502.001.501.000.50 1 2 3 4 5 6 7 8 9 10 11 Quantity ofIce-Cream Cones冰激淋蛋卷的數(shù) 量 $3.00 121. A decrease in price . 2. . increases quantity of cones demanded. Market Demand versus Individual Demand市場需求和單個消費者需求uMarket demand refers to the sum of all individual demands for a particular good or service.市場需求是指所有個人對某種物品或勞務(wù) 需求的總和 uG raphically, individual demand curves are summed horizontally to obtain the market demand curve.u從圖形上看 , 把個人需求曲線水平相加，就得出了市場需求曲線。

Change in Quantity Demanded versus Change in Demand需求量的變化與需求的變化Change in Quantity Demanded(需求量的變化）u Caused by a change in the price of the product.(是由于產(chǎn) 品價格變動引起的 )u Movement along the demand curve.(沿著需求曲線移動) 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.稅收引起冰激凌蛋卷價格上升會導(dǎo) 致沿著需求曲線移動AB 81.00$2.00 4Changes in Quantity Demanded Change in Demand需求的變化uCaused by a change in a determinant other than the price.是由價格以外的因素變化引起的。

uA shift in the demand curve, either to the left or right.需求曲線的移動，向左或者向右 Non-price Determining Variables of Demand需求的非價格決定因素 uConsumer income（消費者的收入）uPrices of related goods（相關(guān) 產(chǎn) 品的價格）替代品 Substitutes 互補品 ComplementsuTastes（ preference）（偏好）uExpectations（預(yù) 期）uNumber of buyers（買者的數(shù) 量） Figure 2 Catherines Demand Schedule and Demand CurvePrice 025.020.015.010.05.0 1 2 3 4 5 6 7 8 9 10 11 Quantity $30.00 12 Consumer Income 消費者收入uAs income increases the demand for a normal good will increase. 收入增加，正常商品的需求增加uAs income increases the demand for an inferior good will decrease. 收入增加，劣等品的需求減少 Shifts in the Demand Curve需求曲線的移動 0 D1 Price of movie Quantity of movieD3 D2Increase in demand需求增加Decrease in demand需求減少 Consumer IncomeNormal Good$3.002.502.001.501.00 0.50 21 3 4 5 6 7 8 9 10 1211Price of Ice-Cream Cone Quantity of Ice-Cream Cones0 Increasein demand An increase in income.D1 D2 消費者收入正常商品$3.002.502.001.501.000.50 21 3 4 5 6 7 8 9 10 1211 冰激凌蛋卷的價格冰激凌蛋卷的數(shù) 量0 需求增加收入增加 .D1 D2 Consumer IncomeInferior Good$3.002.502.001.501.000.50 21 3 4 5 6 7 8 9 10 1211 Price of Ice-Cream Cone Quantity of Ice-Cream Cones0 Decreasein demand An increase in income.D1D2 消費者收入劣等品$3.002.502.001.501.000.50 21 3 4 5 6 7 8 9 10 1211 冰激凌蛋卷的價格冰激凌蛋卷的數(shù) 量0 需求減少收入增加 .D1D2 Prices of Related GoodsSubstitutes & Complements相關(guān) 物品的價格替代品和互補品u When a fall in the price of one good reduces the demand for another good, the two goods are called substitutes.u 當(dāng) 一種物品價格下降減少了另一種物品需求時，這兩種物品被稱為替代品。

u When a fall in the price of one good increases the demand for another good, the two goods are called complements. u 當(dāng) 一種物品價格下降增加了另一種物品需求時，這兩種物品被稱為互補品 Table 1 Variables That Influence Buyers影響消費者需求的因素 Copyright2004 South-Western Supply 供給Quantity supplied is the amount of a good that sellers are willing and able to sell. 供給量是指賣者愿意而且能夠出售的一種物品或勞務(wù) 的數(shù) 量 Law of Supply 供給規(guī) 律The law of supply states that there is a direct (positive) relationship between price and quantity supplied.供給規(guī) 律認(rèn) 為，價格與供給量之間的關(guān) 系是正關(guān) 系。

Supply Schedule 供給表The supply schedule is a table that shows the relationship between the price of the good and the quantity supplied.供給表是表示一種物品價格與供給量之間關(guān) 系的表格 Bens Supply Schedule 供給表Price 價格 Quantity 數(shù) 量 $0.00 0 0.50 0 1.00 1 1.50 2 2.00 3 2.50 4 3.00 5 Supply Curve 供給曲線The supply curve is the upward-sloping line relating price to quantity supplied. 供給曲線把價格與供給量聯(lián) 系在一起的向右上方傾斜的曲線 Figure 5 Bens Supply Schedule and Supply Curve（）rice ofIce-CreamCone 02.502.001.501.00 1 2 3 4 5 6 7 8 9 10 11 Quantity ofIce-Cream Cones$3.00 120.501. Anincrease in price . 2. . increases quantity of cones supplied. Market Supply versus Individual Supply市場供給和單個廠商供給u Market supply refers to the sum of all individual supplies for all sellers of a particular good or service.市場供給是指某種物品或勞務(wù) 的所有賣者個人供給的總和。

u G raphically, individual supply curves are summed horizontally to obtain the market supply curve.u 從圖形上看 , 把個人供給曲線水平相加，就得出了市場供給曲線 Change in Quantity Supplied versus Change in Supply供給量的變化與供給的變化Change in Quantity Suppliedu Movement along the supply curve.u Caused by a change in the market price of the product.供給量的變化 u 沿著供給曲線移動 u 是由于產(chǎn) 品的市場價格變動引起的 Change in Quantity Supplied供應(yīng) 量的變化 1 5 Price of Ice-Cream Cone Quantity of Ice-Cream Cones0 S 1.00 A C$3.00 A rise in the price of ice cream cones results in a movement along the supply curve.冰激淋價格的變化引起了沿著供給曲線移動 Change in Supply供給的變化u A shift in the supply curve, either to the left or right. u Caused by a change in a determinant other than price.u 供給曲線的移動，向左或者向右。

u 是由于價格以外的因素變化造成的 Non-price Determining Variables of Supply供給的非價格決定變量 uInput prices（生產(chǎn) 要素的價格）u勞動 Laboru資本 Capitalu原材料 Raw MaterialsuTechnology（技術(shù) ）uExpectations （預(yù) 期）uNumber of producers（廠商的數(shù) 量） Shifts in the Supply Curve供給曲線的移動Price of steel Quantity0 S1 S2S3Increase in SupplyDecrease in Supplyp0 1051 Table 2 Variables That Influence Sellers Vari abl es A Change i n Thi s Vari abl e . . . Price Represents a movement along the supply curve I nput prices Shifts the supply curve Technology Shifts the supply curve Expectations Shifts the supply curve Number of sellers Shifts the supply curve SUPPLY AND DEMAND TOGETHER供給與需求的結(jié) 合n Equilibrium .i:kwilibrim refers to a situation in which the price has reached the level where quantity supplied equals quantity demanded. 市場均衡價格水平達(dá) 到使供給量與需求量相等的狀態(tài) 。

Supply and Demand Together Price Quantity$0.00 00.50 01.00 1 1.50 42.00 72.50 103.00 13 Price Quantity$0.00 190.50 161.00 13 1.50 102.00 72.50 43.00 1 Demand Schedule Supply ScheduleAt $2.00, the quantity demanded is equal to the quantity supplied!在 $2.00時 , 需求量等于供給量 ! Figure 8 The Equilibrium of Supply and Demand Copyright2003 Southwestern/Thomson Learning Price ofIce-CreamCone 0 1 2 3 4 5 6 7 8 9 10 11 12Quantity of Ice-Cream Cones13EquilibriumQuantity均衡數(shù) 量Equilibrium price均衡價格 Equilibrium均衡 SupplyDemand$2.00 Supply and Demand Together供給與需求的結(jié) 合Equilibrium Price（均衡價格）u The price that balances supply and demand. u On a graph, it is the price at which the supply and demand curves intersect.u 使供給與需求平衡的價格。

u 從圖形上看，就是供給曲線與需求曲線相交時的價格 Equilibrium Quantity（均衡數(shù) 量） u The quantity that balances supply and demand. u On a graph it is the quantity at which the supply and demand curves intersect. u 當(dāng) 價格調(diào) 整到使供給與需求平衡時的供給量與需求量 u 從圖形上看，就是供給曲線與需求曲線相交時的數(shù) 量 Figure 9 Markets Not in EquilibriumPrice ofIce-CreamCone 0 SupplyDemand (a) Excess Supply超額供給 Quantitydemanded QuantitysuppliedSurplus 過剩 Quantity ofIce-CreamCones4$2.50 102.00 7 Equilibrium 均衡n SurplusWhen 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.n 過剩當(dāng) 價格高于均衡價格時，供給量大于需求量。

存在超額供給或過剩供給者通過降低價格來增加銷售，這使價格向其均衡水平變動 Figure 9 Markets Not in EquilibriumPrice ofIce-CreamCone 0 Quantity ofIce-CreamConesSupplyDemand (b) Excess Demand超額需求 Quantitysupplied Quantitydemanded1.50 10$2.00 74 Shortage短缺 Equilibrium 均衡n ShortageWhen 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.n 短缺當(dāng) 價格低于市場均衡價格時，需求量超過了供給量。

存在著超額需求或短缺由于太多賣者要購買太少的物品，供給者將提高價格因此價格將趨向于市場均衡價格 Three Steps To Analyzing Changes in Equilibrium分析均衡變動的三個步驟u Decide whether the event shifts the supply or demand curve (or both).u Decide whether the curve(s) shift(s) to the left or to the right.u Use the supply-and-demand diagram to see how the shift affects equilibrium price and quantity. u 確定該事件是使供給曲線移動，還是使需求曲線移動，或者使兩種曲線都移動 u 確定曲線是向右移動，還是向左移動。

u 用供求圖來考察這種移動如何影響均衡價格和數(shù) 量 How an Increase in Demand Affects the Equilibrium需求增加如何影響均衡Price ofIce-CreamCone2.00 0 7 Quantity ofIce-Cream ConesSupplyInitialEquilibrium原來的均衡 D1 1. Hot weather increasesthe demand for ice cream.天氣熱使冰激凌需求增加D 22. .resultingin a higherprice. $2.50 103. .and a higherquantity sold. New equilibrium新均衡 S2How a Decrease in Supply Affects the EquilibriumPrice ofIce-CreamCone2.000 1 2 3 4 7 8 9 11 12 Quantity of Ice-Cream Cones13 DemandInitial equilibriumS110 1. An increase in the priceOf sugar reduces the Supply of ice cream.Newequilibrium2. .resultingin a higherprice. $2.50 3. .and a lowerquantity sold. S2How a Decrease in Supply Affects the EquilibriumPrice ofIce-CreamCone2.000 1 2 3 4 7 8 9 11 12 Quantity of Ice-Cream Cones13 D1Initial equilibriumS110 1. An increase in the priceOf sugar reduces the Supply of ice cream.2. .resultingin a higherprice. 3. .and a lowerquantity sold. D2Newequilibrium Summaryn 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 include income, the prices of complements and substitutes, tastes, expectations, and the number of buyers.If one of these factors changes, the demand curve shifts. 小結(jié)n 需求曲線表示一種物品的需求量如何取決于價格。

根據(jù) 需求規(guī) 律，當(dāng) 一種物品價格上升時，需求量減少所以需求曲線是下傾的除了價格以外，決定需求量的其它因素包括收入、替代品和互補品的價格、嗜好、預(yù) 期，以及買者的數(shù) 量如果這些變量中的任何一個變化，導(dǎo) 致需求曲線移動 Summaryn 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 include input prices, technology, expectations, and the number of sellers.If one of these factors changes, the supply curve shifts. 小結(jié)n 供給曲線表示一種物品的供給量如何取決于價格。

根據(jù) 供給規(guī) 律，當(dāng) 一種物品的價格上升時，供給量增加所以供給曲線是上傾的除了價格以外，決定供給量的其它因素包括投入要素的價格、技術(shù) 、預(yù) 期，以及賣者的數(shù) 量如果這些變量中的任何一個變化，導(dǎo) 致供給曲線移動 Summaryn Market equilibrium is determined by the intersection of the supply and demand curves.n At the equilibrium price, the quantity demanded equals the quantity supplied.n The behavior of buyers and sellers naturally drives markets toward their equilibrium. 小結(jié)u市場均衡是由供給曲線和需求曲線相交決定的 n 在均衡價格水平上，需求量和供給量相等。

n 買者和賣者的行為自然地驅(qū) 動市場走向均衡 Summaryn To analyze how any event influences a market, we use the supply-and-demand diagram to examine how the even affects the equilibrium price and quantity.n In market economies, prices are the signals that guide economic decisions and thereby allocate resources. 小結(jié)n 為了分析一個事件如何影響市場，我們利用供求圖來考察這一事件如何影響均衡價格和均衡數(shù) 量 n 在市場經(jīng) 濟中，價格是指引經(jīng) 濟決策從而配置稀缺資源的信號。

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