07消费者、生产者与市场效率

nullnullChapter 7 Consumers, Producers, And The Efficiency Of MarketsnullWillingness to pay: the maximum amount that a buyer will pay for a good. Consumer surplus: is the amount a buyer is willing to pay for a good minus the amount the buyer actually pays for it. (N.Gregory Mankiw, Principles of Economics(2004), third edition, Chapter 7, pp138-143.) 7.1. Consumer surplusnull消费者购买一定数量商品意愿支付的货币量与实际支付货币量之间存在的差额称为消费者剩余(Consumer surplus)。存在消费者剩余，是因为需求曲线向下倾斜，意味着消费者购买的第一单位商品比最后一单位商品对他具有更大效用和价值，他本来愿意为第一和比较靠前的那些商品支付更多的钱，但是由于存在普遍市场价格，他不必这样做,于是有了消费者剩余. Consumer surplusnullFour Possible Buyer’s Willingness to PaynullTable7-1 The Demand Table. This table shows the demand schedule for the buyer in table 1.nullFigure7-1 The Demand Curve. This graph shows the corresponding demand curve. Note that the height of the demand curve reflects buyers’ willingness to pay.nullFigure7-2 Measuring Consumer Surplus With The Demand Curve. In panel (a), the price of the good is $80, and the consumer surplus is $20.nullFigure7-2 Measuring Consumer Surplus With The Demand Curve. In panel (b), the price of the good is $70, and the consumer surplus is $40.Using the Demand Curve to Measure Consumer SurplusUsing the Demand Curve to Measure Consumer SurplusThe area below the demand curve and above the price measures the consumer surplus in the market.Figure 3 How the Price Affects Consumer SurplusFigure 3 How the Price Affects Consumer SurplusCopyright©2003 Southwestern/Thomson LearningQuantity(a) Consumer Surplus at Price PPrice0Figure 3 How the Price Affects Consumer SurplusFigure 3 How the Price Affects Consumer SurplusCopyright©2003 Southwestern/Thomson LearningQuantity(b) Consumer Surplus at Price PPrice0What Does Consumer Surplus Measure?What Does Consumer Surplus Measure?Consumer surplus, the amount that buyers are willing to pay for a good minus the amount they actually pay for it, measures the benefit that buyers receive from a good as the buyers themselves perceive it.nullProducer surplus is the amount a seller is paid for a good minus the seller’s cost. It measures the benefit to sellers participating in a market. Cost: the value of everything a seller must give up to produce a good. Producer surplus: is the amount a seller is paid for a good minus the cost of production. (N.Gregory Mankiw, Principles of Economics(2004), third edition, Chapter 7, pp143-147.) 7.2. Producer surplusnullFigure 4 The Supply Schedule and the Supply CurveFigure 4 The Supply Schedule and the Supply CurveUsing the Supply Curve to Measure Producer SurplusUsing the Supply Curve to Measure Producer SurplusThe area below the price and above the supply curve measures the producer surplus in a market.Figure 5 Measuring Producer Surplus with the Supply CurveFigure 5 Measuring Producer Surplus with the Supply CurveCopyright©2003 Southwestern/Thomson LearningQuantity ofHouses PaintedPrice ofHousePainting500800$90006001234(a) Price = $600Figure 5 Measuring Producer Surplus with the Supply CurveFigure 5 Measuring Producer Surplus with the Supply CurveCopyright©2003 Southwestern/Thomson LearningQuantity ofHouses PaintedPrice ofHousePainting500800$90006001234(b) Price = $800Figure 6 How the Price Affects Producer SurplusFigure 6 How the Price Affects Producer SurplusCopyright©2003 Southwestern/Thomson LearningQuantity(a) Producer Surplus at Price P Price0Figure 6 How the Price Affects Producer SurplusFigure 6 How the Price Affects Producer SurplusCopyright©2003 Southwestern/Thomson LearningQuantity(b) Producer Surplus at Price P Price0P1BCSupplyAInitialproducersurplusQ1null7.3. Market Efficiency 7.3.1. The Benevolent Social PlannerConsumer surplus=Value to buyers – Amount paid by buyers Producer surplus = Amount received by sellers – Costs of sellers Total surplus = Consumer surplus + Producer surplus = Value to buyers – Costs of sellers MARKET EFFICIENCYMARKET EFFICIENCYEfficiency is the property of a resource allocation of maximizing the total surplus received by all members of society. In addition to market efficiency, a social planner might also care about equity – the fairness of the distribution of well-being among the various buyers and sellers. Figure 7 Consumer and Producer Surplus in the Market EquilibriumFigure 7 Consumer and Producer Surplus in the Market EquilibriumCopyright©2003 Southwestern/Thomson LearningPrice0QuantityMARKET EFFICIENCY MARKET EFFICIENCY Three Insights Concerning Market Outcomes Free markets allocate the supply of goods to the buyers who value them most highly, as measured by their willingness to pay. Free markets allocate the demand for goods to the sellers who can produce them at least cost. Free markets produce the quantity of goods that maximizes the sum of consumer and producer surplus. (Mankiw, Principles of Economics(2004), third edition, chapter7, p149.)Figure 8 The Efficiency of the Equilibrium QuantityFigure 8 The Efficiency of the Equilibrium QuantityCopyright©2003 Southwestern/Thomson LearningQuantityPrice0Figure 7-8 The Efficiency of the Equilibrium Quantity. At quantities less than the equilibrium quantity, the value to buyers exceeds the cost to sellers. At quantities greater than the equilibrium quantity, the cost to sellers exceeds the value to buyers; Therefore, the market equilibrium maximizes the sum of producer and consumer surplus. 7.3.2 Evaluating the Market Equilibrium7.3.2 Evaluating the Market EquilibriumBecause the equilibrium outcome is an efficient allocation of resources, the social planner can leave the market outcome as he/she finds it. This policy of leaving well enough alone goes by the French expression laissez faire.7.3.2 Evaluating the Market Equilibrium 7.3.2 Evaluating the Market Equilibrium Market Power If a market system is not perfectly competitive, market power may result. Market power is the ability to influence prices. Market power can cause markets to be inefficient because it keeps price and quantity from the equilibrium of supply and demand.7.3.2 Evaluating the Market Equilibrium 7.3.2 Evaluating the Market Equilibrium Externalities created when a market outcome affects individuals other than buyers and sellers in that market. cause welfare in a market to depend on more than just the value to the buyers and cost to the sellers. When buyers and sellers do not take externalities into account when deciding how much to consume and produce, the equilibrium in the market can be inefficient.SummarySummaryConsumer surplus equals buyers’ willingness to pay for a good minus the amount they actually pay for it. Consumer surplus measures the benefit buyers get from participating in a market. Consumer surplus can be computed by finding the area below the demand curve and above the price.SummarySummaryProducer surplus equals the amount sellers receive for their goods minus their costs of production. Producer surplus measures the benefit sellers get from participating in a market. Producer surplus can be computed by finding the area below the price and above the supply curve.SummarySummaryAn allocation of resources that maximizes the sum of consumer and producer surplus is said to be efficient. Policymakers are often concerned with the efficiency, as well as the equity, of economic outcomes.SummarySummaryThe equilibrium of demand and supply maximizes the sum of consumer and producer surplus. This is as if the invisible hand of the marketplace leads buyers and sellers to allocate resources efficiently. Markets do not allocate resources efficiently in the presence of market failures.nullCase study: Should there be a market in organs?On April 12, 2001, the front page of The Boston Globe ran the headline “How a Mother’s Love Helped Save Two Lives.” The newspaper told the story of Susan Stephens, a woman whose son needed a kidney transplant. When the doctor learned that the mother’s kidney was not compatible, he proposed a novel solution: If Stephens donated one of her kidneys to a stranger, her son would move to the top of the kidney waiting list. The mother accepted the deal, and soon two patients had the transplant they were waiting for. The ingenuity of the doctor’s proposal and the nobility of the mother’s act cannot be doubted. But the story raises many intriguing questions. If the mother could trade a kidney for a kidney, would the hospital allow her to trade a kidney for an expensive, experimental cancer treatment that she could not afford otherwise? Should she be allowed to exchange her kidney for free tuition for her son at the hospital’s medical school?nullCase study: Should there be a market in organs?As a matter of public policy, people are not allowed to sell their organs. In essence, in the market for organs, the government has imposed a price ceiling of zero. The result, as with any binding price ceiling, is a shortage of the good. Many economists believe that there would be large benefits to allowing a free market in organs. People are born with two kidneys, but they usually need only one. Meanwhile, a few people suffer from illnesses that leave them without any working kidney. Such a market would lead to an efficient allocation of resources, but critics of this plan worry about fairness. A market for organs, they argue, would benefit the rich at the expense of the poor, because organs would then be allocated to those most willing and able to pay. But you can also question the fairness of the current system. Now, most of us walk around with an extra organ that we don’t really, while some of our fellow citizens are dying to get one. Is that fair?Mankiw-Ch.7: ProblemMankiw-Ch.7: Problem生产者剩余与生产者的利润是不是一样的，请说明理由？ Producer surplus= Amount received by sellers – Cost to sellers.null计算：某商品的供给函数，Q=30+p/3,当价格从3元上升到9元时，生产者剩余增加了多少(看图)?Chapter7. Problems and ApplicationsnullnullnullChapter5-4. Why is it wrong to say, “Utility is maximized when the marginal utilities of all goods are exactly equal?” Correct the statement and explain.(Samuelson, Economics, 17th , p100.) Answer: It is the ratio of marginal utility to price that is constant over all good in equilibrium. nullChapter5-9. An interesting application of supply and demand to addictive substances compares alternative techniques for supply restriction. For this problem, assume that the demand for addictive substances is inelastic. (Samuelson, Economics, 17th edition, p100.) One approach (used today for heroin and cocaine and for alcohol during Prohibition) is to reduce supply at the nation’s borders. Show how this raises price and increases the total income of the suppliers in the drug industry. An alternative approach (followed today for tobacco and alcohol) is to tax the goods heavily. Using the tax apparatus, show how this reduces the total income of the suppliers in the drug industry. nullnull Chapter5-11. Assume that the demand for travel over a bridge takes the form Y=1,000,000 – 50,000P, where Y is the number of trips over the bridge and P is the bridge toll (in dollars). (Samuelson, 17th edition, p101.) Calculate the consumer surplus if the bridge toll is $0, $1, and $20. Assume that the cost of the bridge is $1,800,000. Calculate the toll that will just break even. What is the consumer surplus at the break-even toll? Assume that the cost of the bridge is $8 million. Explain why the bridge should be built even though there is no toll that will cover the cost. null1,000,000Y$20POAC$1pBDY = 20,000Y=1,000,000-50,000P$pnullAnswer Chapter5-11: a. Consumer surplus When the bridge toll=$0, Consumer surplus = 1/2  1,000,00020=10,000,000; By triangle rule, p/20=y/1,000,000,then y = 50,000p, when the bridge toll, p=$1, y = 50,000, Consumer surplus = 1/2(1,000,000-50,000)(20-1)=9,025,000; When the bridge toll=$20, Consumer surplus = 0 nullb. 根据三角形原理：p/20=y/1,000,000，则y=50,000p 　p(1,000,000-50,000p)=1,800,000 p2-20p+36=0 得：p1=18, 　或　p2=2. 　(1) When p1=18, 得y1= 50,000p = 900,000, 　　(1,000,000-900,000)=100,000 　the consumer surplus at the break-even toll 　＝1/2 100,000 (20-18)=100,00; 　(2) When p2=2, 得y2= 50,000p = 100,000, 　　(1,000,000-100,000)=900,000 　the consumer surplus at the break-even toll 　＝1/2 900,000 (20-2)=8,100,00; nullc. 根据三角形原理：p/20=y/1,000,000，则y=50,000p 　p(1,000,000-50,000p)=8,000,000 p2-20p+160=0 p值无解，即过桥费无法弥补桥梁的成本。 For the bridge is public goods that maximize utilities of common people, the bridge should be built even though there is no toll that will cover the cost nullAppendix 5 Geometrical Analysis of consumer EquilibriumThe Indifference Curve The point on the indifference curve represent consumption bundles among which the consumer is indifference; all are equally desirable. 表 关于同志近三年现实表现材料材料类招标技术评分表图表与交易pdf视力表打印pdf用图表说话 pdf 示偏好的无差异曲线：表示给消费者相同满足程度的消费组合的一条曲线nullLaw of Substitution The scarce a good, the greater its relative substitution value; its marginal utility rises relative to the marginal utility of the good that has become plentiful. The slope of the indifference curve is the measure of the goods’ relative marginal utilities, or of the substitution terms on which-- for very small changes– the consumer would be willing to exchange a little less of one good in return for a little more of the other. nullAn indifference curve that is convex(凸的) in the manner of Fig5A-1 conforms to the law of substitution. As the amount of food you consume goes up -- and the quantity of clothing goes down – food must become relatively cheaper in order for you to be persuaded to take a little extra food in exchange for a little sacrifice of clothing. The precise shape and slope of an indifference curve will, of course, vary from one consumer to the next, but the typical shape will take the form shown in Fig 5A-1. nullnull无差异曲线的斜率可以用 MUFood / MUClothing 来表示,即横轴上商品（Food）的相对边际效用。null无差异曲线凸向原点，表示曲线从左到右斜率绝对值越变越小，即边际替代率(substitution ratio, sometimes called the marginal rates of substitution)越变越小. 一条无差异曲线上任意一点的斜率等于消费者愿意用一种物品代替另一种物品的比率。这个比率称为边际替代率（the marginal rate of substitution, MRS） MRS递减经济含义是，当大量消费食物来替代服装消费时，食物的边际效用会下降；大量消费服装来替代消费食物时，服装的边际效用会下降。因而，食物和服装组合应当“适当”。 null　(1)斜率为负 通常物品的效用是正的。因此，如果要增加一种物品的消费数量，为了使消费者的满足程度不变就要减少另一种物品的消费数量。 (2)离原点越远，效用越大 消费者通常对数量多的物品组合的偏好大于数量少的组合。也就是说，对于消费者来说，消费量越大（无差异曲线离原点越远）效用越大。5A-2.无差异曲线的特征null　(3)无差异曲线不相交 　　假设两条无差异曲线相交。由于A和B在同一条无差异曲线上，两点的效用相同。B和C也位于同一条无差异曲线上，因此B和C的效用也相同。这意味着尽管C点两种物品都比A点多，但A和C具有相同的效用。这显然与消费者对两种物品的消费越多效用越大的假设相矛盾。null（4）无差异曲线凸向原点 由于边际效用递减规律，随着人们对一种物品消费量的增加，他们不得不放弃的另一种物品的消费量会越来越大。 null（1）完全替代品：无差异曲线为直线的两种物品。 （2）完全互补品：无差异曲线为直角的两种物品。5A-3.两种极端的无差异曲线的例子5A-4. 消费者的预算约束 5A-4. 消费者的预算约束 预算约束曲线:对消费者可以承受的消费组合的限制。 预算线：Y=PAQA+PBQB，其中Y代表收入，PA、PB分别为商品A和B的价格，QA和QB分别是购买量。 预算线斜率： PA/ PB ,横轴上商品（A）的相对价格。 5A-4.预算约束曲线的变动 5A-4.预算约束曲线的变动 收入：收入增加（减少）时预算集扩大（缩小），表现为预算约束曲线向外（内）平移。 null价格：价格上升（下降）预算集缩小（扩大），表现为预算约束曲线在价格变动的商品一端的内（外）移。 5A-4. 预算约束曲线的变动 null Put differently,the substitution ratio, or the slope of the indifference curve, is the ratio of the marginal utility of food to the marginal utility of clothing. So tangency condition is just another way of stating that the ratio of prices must be equal to the ratio of marginal utilities; in equilibrium, the consumer is getting the same marginal utility from the last penny spent on food as from the last penny spent on clothing. Therefore, equilibrium condition is (Mankiw, the Principles of Economics, 3th edition, chapter21, p462.):5A-5.the Equilibrium Position of tangentnullA.选择目标：实现效用最大化。 B.预算约束下的消费者选择 无差异曲线与预算线相切时，消费者达到最大效用。因此，效用最大化的条件是：无差异曲线的斜率（MUA/MUB）等于预算线的斜率（PA/PB），或用 MUA / PA ＝ MUB / PB 表示，即消费者选择的两种物品的组合要使每一元所带来的边际效用相等5A-5.消费者选择null5A-5.预算约束下的消费者选择null当收入和其他商品的价格保持不变时，对一种商品的最优选择（效用最大化时的选择）会随着该商品的价格变动而变动。表示这些价格与选择量变动的曲线就是“需求曲线”。需求曲线实际上是消费者在各种不同价格下最优选择变动的轨迹。5A-5.需求曲线的导出null5A-5. Deriving demand curve (Mankiw, the Principles of Economics, 3th edition, chapter21-figure11,p467.)