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1、-微观经济学-第 6 页1.为什么长期需求弹性与短期需求弹性会有不同？考虑两种商品：纸巾和电视机。哪一种是耐用品？你觉得纸巾的短期需求弹性大，还是长期需求弹性大？为什么？电视机的需求弹性又是怎样的呢？长期需求弹性与短期需求弹性的不同是基于人们对价格变化的敏感反映程度和可替代品数量的多少。对于大多数商品，长期需求远比短期需求富有价格弹性，因为人们要需要较长的时间来改变他的消费习惯。纸巾是非耐用品，如果纸巾的价格上升，在短期消费者无法改变使用纸巾的习惯，短期弹性较小，而在长期，纸巾的需求会随着新的替代品的进入而变的更加有弹性。所与之相反，耐用品的更新换代时间较长，当耐用品的价格上涨时，在短期的需求
2、量会随价格的上升而迅速下降，结果长期需求弹性要小于短期需求弹性。2.Explain why an MRS between two goods must equal the ratio of the price of the goods for the consumer to achieve maximum satisfaction.The MRS describes the rate at which the consumer is willing to trade one good for another to maintain the same level of satisfaction.
3、 The ratio of prices describes the trade-off that the market is willing to make between the same two goods. The tangency of the indifference curve with the budget line represents the point at which the trade-offs are equal and consumer satisfaction is maximized. If the MRS between two goods is not e
4、qual to the ratio of prices, then the consumer could trade one good for another at market prices to obtain higher levels of satisfaction. For example, if the slope of the budget line (the ratio of the prices) is 4 then the consumer can trade 4 units of good 2 for one unit of good 1. If the MRS at th
5、e current bundle is 6, then the consumer is willing to trade 6 units of good 2 for one unit of good 1. Since the two slopes are not equal the consumer is not maximizing her satisfaction. The consumer is willing to trade 6 but only has to trade 4, so she should make the trade. This trading continues
6、until the highest level of satisfaction is achieved. As trades are made, the MRS will change and become equal to the price ratio.3.等产量线可能是凸的、线性的或者L形的。各种形状的等产量线代表了什么性质的生产函数？又意味着什么样的边际技术替代率？等产量线是由生产出同一产量的不同投入品组合形成的曲线。凸的等产量线表明边际技术替代率递减，任何一种投入品的生产率都是有限的。如果等产量线是线性的，说明两种投入品之间是完全可替代的，此时边际技术替代率在等产量线上的所有点均为常
7、数。如果等产量线是L型的，此时投入品之间不能进行任何替代，投入品只有按相同比例递增，在L型等产量线的垂直部分和水平部分，投入品的边际产出均为零。4.Assume the marginal cost of production is increasing. Can you determine whether the average variable cost is increasing or decreasing? Explain.Marginal cost can be increasing while average variable cost is either increasing or
8、 decreasing. If marginal cost is less (greater) than average variable cost, then each additional unit is adding less (more) to total cost than previous units added to the total cost, which implies that the AVC declines (increases). Therefore, we need to know whether marginal cost is greater than ave
9、rage variable cost to determine whether the AVC is increasing or decreasing.5. Why would a firm that incurs losses choose to produce rather than shut down?Losses occur when revenues do not cover total costs. Revenues could be greater than variable costs, but not total costs, in which case the firm i
10、s better off producing in the short run rather than shutting down, even though they are incurring a loss. The firm should compare the level of loss with no production to the level of loss with positive production, and pick the option that results in the smallest loss. In the short run, losses will b
11、e minimized as long as the firm covers its variable costs. In the long run, all costs are variable, and thus, all costs must be covered if the firm is to remain in business.6.Can there be constant returns to scale in an industry with an upward-sloping supply curve? Explain.Constant returns to scale
12、imply that proportional increases in all inputs yield the same proportional increase in output. Proportional increases in inputs can induce higher prices if the supply curves for these inputs are upward sloping. For example, production that uses rare or depleting inputs will see higher costs of prod
13、uction as production increases in scale. Doubling inputs will still yield double output, but because of rising costs, the firm cannot offer increasing amounts of the good without higher prices. Therefore, constant returns to scale does not always imply long-run horizontal supply curves.7.Suppose the
14、 government wants to limit imports of a certain good. Is it preferable to use an import quota or a tariff? Why?Changes in domestic consumer and producer surpluses are the same under import quotas and tariffs. There will be a loss in (domestic) total surplus in either case. However, with a tariff, th
15、e government can collect revenue equal to the tariff times the quantity of imports and these revenues can be redistributed in the domestic economy to offset the domestic deadweight loss by, for example, reducing taxes. Thus, there is less of a loss to the domestic society as a whole. With the import
16、 quota, foreign producers can capture the difference between the domestic and world price times the quantity of imports. Therefore, with an import quota, there is a loss to the domestic society as a whole. If the national government is trying to increase welfare, it should use a tariff.8.Why does a
17、tax create a deadweight loss? What determines the size of this loss?A tax creates deadweight loss by artificially increasing price above the free market level, thus reducing the equilibrium quantity. This reduction in demand reduces consumer as well as producer surplus. The size of the deadweight lo
18、ss depends on the elasticities of supply and demand. As the elasticity of demand increases and the elasticity of supply decreases, i.e., as supply becomes more inelastic, the deadweight loss becomes larger.9.为什么在垄断下没有市场供给曲线？垄断性市场不存在一个价格和产量之间的一一对应关系，原因在于垄断者的产量不仅取决于边际成本，而且也取决于需求曲线的形状。需求的变动给出了一系列价格和产量，
19、需求的变动也可以导致价格改变但产量不变，产量改变而价格不变，或两者都改变。10.Why is there a social cost to monopoly power? If the gains to producers from monopoly power could be redistributed to consumers, would the social cost of monopoly power be eliminated? Explain briefly.When the firm exploits its monopoly power by charging a pric
20、e above marginal cost, consumers buy less at the higher price. Consumers enjoy less surplus, the difference between the price they are willing to pay and the market price on each unit consumed. Some of the lost consumer surplus is not captured by the seller and is a deadweight loss to society. There
21、fore, if the gains to producers were redistributed to consumers, society would still suffer the deadweight loss.10.Show why optimal, third-degree price discrimination requires that marginal revenue for each group of consumers equals marginal cost. Use this condition to explain how a firm should chan
22、ge its prices and total output if the demand curve for one group of consumers shifted outward, so that marginal revenue for that group increased. We know that firms maximize profits by choosing output so marginal revenue is equal to marginal cost. If MR for one market is greater than MC, then the fi
23、rm should increase sales to maximize profit, thus lowering the price on the last unit and raising the cost of producing the last unit. Similarly, if MR for one market is less than MC, the firm should decrease sales to maximize profit, thereby raising the price on the last unit and lowering the cost
24、of producing the last unit. By equating MR and MC in each market, marginal revenue is equal in all markets.一组转向另一组。If the quantity demanded increased, the marginal revenue at each price would also increase. If MR = MC before the demand shift, MR would be greater than MC after the demand shift. To lo
25、wer MR and raise MC, the producer should increase sales to this market by lowering price, thus increasing output. This increase in output would increase MC of the last unit sold. To maximize profit, the producer must increase the MR on units sold in other markets, i.e., increase price in these other
26、 markets. The firm shifts sales to the market experiencing the increase in demand and away from other markets.11.The kinked demand curve describes price rigidity. Explain how the model works. What are its limitations? Why does price rigidity arise in oligopolistic markets?According to the kinked-dem
27、and curve model, each firm faces a demand curve that is kinked at the currently prevailing price. If a firm raises its price, most of its customers would shift their purchases to its competitors. This reasoning implies a highly elastic demand for price increases. If the firm lowers its price, howeve
28、r, its competitors would also lower their prices. This implies a demand curve that is more inelastic for price decreases than for price increases. This kink in the demand curve implies a discontinuity in the marginal revenue curve, so only large changes in marginal cost lead to changes in price. How
29、ever accurate it is in pointing to price rigidity, this model does not explain how the rigid price is determined. The origin of the rigid price is explained by other models, such as the firms desire to avoid mutually destructive price competition.在寡头市场上，由于囚徒的困境，不公开的串通是很脆弱的，而且，厂商之间为了避免价格战而导致亏本，所以即使成本
30、或需求改变了，也不太愿意改变价格，以免给竞争者造成错觉，导致价格竞争。因此，寡头市场上价格具有刚性。12.Why might a labor supply curve be backward bending?A backward-bending supply curve for labor may occur when the income effect of an increase in the wage rate dominates the substitution effect. Labor supply decisions are made by individuals choosin
31、g the most satisfying combination of work and other (leisure) activities. With a larger income, the individual can afford to work fewer hours: the income effect. As the wage rate increases, the value of leisure time (the opportunity cost of leisure) increases, thus inducing the individual to work lo
32、nger hours: the substitution effect. Because the two effects work in opposite directions, the shape of an individuals labor supply curve depends on the individuals preferences for income, consumption, and leisure.13.How does the utility possibilities frontier relate to the contract curve?Since each
33、point in an Edgeworth box can be compared to every other point by each individual, individuals can assign a preference ordering to all points. This preference ordering is the utility function. We can graph these preferences with levels of satisfaction (utility) for one individual on one axis and lev
34、els of satisfaction for a second individual on the other axis. (Of course, more than two individuals can be represented with more axes.) The utility-possibility frontier shows the levels of satisfaction achieved by each of two individuals when they have traded to an efficient outcome on the contract
35、 curve. While points that lie between the origin and the utility-possibility frontier are feasible they are not efficient because further trading will leave one individual better off without making the other individual worse off. Points outside the frontier are not feasible unless the individuals ar
36、e given greater amounts of one or both goods.14.How is the production-possibilities frontier related to the production contract curve?We can graph the quantities of each good produced (each point in the Edgeworth box) on a two-dimensional graph, where the vertical axis represents the output of one g
37、ood and the horizontal axis represents the output of the other good. The production-contract curve is represented in this two-dimensional graph as the production possibilities frontier. Points inside this frontier are feasible but inefficient. Points outside the frontier are infeasible and only atta
38、inable when more inputs become available or production processes become more efficient. Points on the production-possibilities frontier are the same as those on the production-contract curve. The difference is that the production-contract curve measures inputs on the axes and the production-possibil
39、ities frontier measures outputs on the axes.15.George and Stan live next door to each other. George likes to plant flowers in his garden, but every time he does, Stans dog comes over and digs them up. Since it is Stans dog that is causing the damage, if economic efficiency is to be achieved, it is n
40、ecessary that Stan pay to put up a fence around his yard to keep the dog in. Agree or disagree? Explain.If there are leash laws then this would be true. Stan would either need to keep his dog on a leash or put up a fence. In general, it is possible for the two parties to bargain and come up with a s
41、olution that will benefit both of them. They could for example split the cost of the fence. Economic efficiency does not require that Stan pay for the fence. It merely requires that Stan and George negotiate over how best to address the problem and come up with a solution that will work for both of them.