中级微观经济学复习

中级微观经济学复习Budget constraint预算约束Consumption bundles: a list of numbers of goods and services the objects of consumers choice. 消费束：一系列商品和服务的组合,消费者选择的东西。消费束是我们研究选择问题中涉及到的全部商品（或服务）The budget set of the consumer: the consumers affordable consumption bundles, (x1, x2) satisfying p1x1 + p2x2 m.预算集：既定价格和收入下消费者能负担得起的所有消费束的集合。Composite good: take x2 as everything else, the dollars spent on other goods.复合商品: 它代表除商品1之外所有其他的消费品Budget line: the set of bundles that cost exactly m :p1x1 + p2x2 = m预算线:是指恰好将收入m 花费完的预算集预算线的斜率： 为了多消费一些商品1，你必须放弃一些商品2 的消费。放弃消费商品2 的机会是多消费商品1 的经济成本，这样的经济成本以预算线的斜率衡量预算线的变动Budget Line Changes：Change in income收入增加会使预算线向外平行移动，收入下降会使预算线向内平行移动。Changes in prices商品1 价格上升，预算线会变得更陡峭，商品2 价格上升，预算线会变得更平缓观点：完全平衡的通货膨胀（即所有商品价格和收入都按相同比率上升），不会改变任何人的预算集，因此也不会改变任何人的最优选择。(tp1)x1 + (tp2)x2 = tmPreference 偏好Consumer Preferences：Consumer ranks consumption bundles by his satisfaction from use of goods, irrelevant to the prices.消费者偏好：，消费者按照自身意愿对两个消费束排序，而并不依赖于价格。: strictly preferred（严格偏好于） : indifferent （无差异）: weakly preferred （弱偏好于）偏好假设：1：完备性公理：A=B或B=A或AB2：反身性公理：A=A3：传递性公理：A=B，B=C，则A=CWeakly preferred set: all of the consumption bundles that are weakly preferred to (x1, x2).弱偏好集：所有弱偏好于(x1, x2)消费组合的消费束良好偏好假设：Monotonicity （单调性）：在讨论的范围内消费商品越多越好Convexity （凸性）：平均消费束弱偏好于端点消费束Indifference curves（无差异曲线）: -The boundary of weakly preferred set; -The bundles for which the consumer is just indifferent to (x1, x2).无差异曲线：弱偏好集的边界，恰好与(x1,x2)无差异的消费束集合。表示不同偏好水平的无差异曲线不可能相交Perfect Substitutes（完全替代品）不满足凸性Perfect Complements（完全互补品）不满足凸性和单调性Discrete Goods（离散商品）Marginal rate of substitution (MRS): slope of an indifference curve. 边际替代率：无差异曲线的斜率，MRS 衡量某消费者恰好愿意以一种商品替代另外一种商品的比率。衡量消费者愿意支付一定数量的商品2 来购买边际数量（即少许）的商品1。边际替代率递减：随着商品1 数量的增多，每增加一单位商品1，消费者愿意放弃商品2 的数量是递减的。或者反过来说，即随着商品1 数量的增多，为了多得到一单位商品2，消费者愿意放弃商品1 的数量是递增的。你拥有某种的数量越多，你越愿意放弃一些这种商品，用来交换其他商品。MRS = Utility 效用Utility ：a numeric measure of a persons happiness. 效用：衡量一个人幸福程度的数值方法Utility function: a way of assigning a number to every possible consumption bundle.效用函数：是为每一个可能的消费束指派一个数字的方法。更受偏好的消费束，赋值越大。Summarize: a monotonic transformation of a utility function is a utility function that represents the same preferences as the original utility function.总结：单调变换前后的效用函数的偏好相同。Cardinal utility（基数效用）: it measures the magnitude of satisfaction.Marginal utility（边际效用）: The ratio that measures the rate of change in utility associated with a small change in the amount of good 1Marginal Utility and MRS边际效用单调变换不会改变边际替代率。Choice 选择Optimal Choice：choose the best bundle the the consumer can afford.The utility maximization problem: such that p1x1+ p2x2 = mMRS = = Another form of optimal condition= Demand function（需求函数）: function relating the optimal choice to the different values of prices and incomes.需求函数：将最优选择与不同的价格和收入联系起来的函数。Demand 需求Demand function：x1=x1(p1, p2, m)；x2=x2(p1, p2, m)Comparative statics (比较静态) :Statics - not concerned with any adjustment process involved in moving from one choice to another.Comparative - to compare two situations: before and after the change in the economic environment.比较静态分析：比较经济变动前后的两种状态，同时只考虑均衡选择，并不关注任何涉及从一种选择到另一种选择的调整过程。所要研究的问题是：当价格和收入发生变动时，需求怎样变动。Normal good : The demand for it would increase when income increases正常商品：当收入增加，对商品的需求也增加的商品。Luxury good（奢侈品）Necessary good（必需品）Inferior good: an increase of income results in a reduction in the consumption of it. 低档商品：收入的增加导致对该商品的需求减少的商品。正常商品和低档商品所考虑的均是收入变化引起的需求变化。Income offer curve: the bundles of goods that are demanded at the different levels of income.收入提供曲线：当预算线平行向外移动，将一系列的需求束连接起来，构成收入提供曲线，表示价格不变的条件下，不同收入水平上的最优选择。Engel curve: a graph of the demand for one of the goods as a function of income, with all prices being held constant. 恩格尔曲线：所有价格保持不变时，单一商品的需求随着收入的变动情况曲线。Ordinary good: the quantity demanded of good 1 should increase when its price decreases.普通商品：价格上升，需求降低的商品Giffen good: decrease in the price of good 1 leads to a reduction in the demand for it. 吉芬商品：价格上升，需求反而上升，或者价格降低，需求也降低的商品。普通商品和吉芬商品都是由于价格变化引起的需求变化。Price offer curve: the connection of the bundles demanded and prices for good 1.价格提供曲线：商品1的价格发生变动而商品2 的价格和收入不变，预算线转动得到一系列最优点，连接起来构成价格提供曲线。Demand curve: the plot of the demand function x1(p1, p2, m), holding p2 and m fixed at some predetermined values.需求曲线：商品2 的价格和收入不变，商品1价格变化下对应的不同最优消费水平。Substitute: good 1 is a substitute for good 2 if and Complement: good 1 is a complement to good 2 if and 假设商品2是普通商品。反需求函数：测度的是消费者消费某个既定数量时的价格。在给定的消费水平上，需求曲线的高度测度的是消费者对于1单位额外商品的边际支付意愿。为了使消费者选择这个消费水平，商品所必须具有的那个价格Reservation price (保留价格) rn: the price at which the consumer is just indifferent to consuming n 1 units or consuming n units of the good. 保留价格：是消费者消费或者不消费某种商品刚好无差异的价格。测度的是对导致消费者增加一单位商品消费所必须的效用增量。Slutsky Equation斯勒茨基方程The Substitution Effect：the change in demand due to the change in the rate of exchange between the two goods替代效应：由于两个商品之间的交换比率的变化引起的需求变化。the income effect：the change in demand due to having more purchasing power收入效应:由于购买力提高而引起的需求变化。价格变动划分为两个步骤：1、相对价格发生变化，同时调整货币收入保持购买力不变；2、对购买力进行调整，是相对价格保持不变。Slutsky identity(斯勒茨基等式): normal good： inferior good： (-) (-) (-) (?) (-) (+)Giffen case: the total change in demand could be positive.A Giffen good must be an inferior good. But an inferior good is not necessarily a Giffen good.The Law of Demand: If the demand for a good increases when income increases, then the demand for that good must decrease when its price increases.需求法则：如果一种商品的需求随着收入的增加而增加，那么这种商品的需求一定做着价格的上升而下降。Consumer surplus消费者剩余消费者剩余：v(n) pn，测度的是消费n单位商品的净效益，由总效用减去对其他商品消费的支出。是使消费者放弃对某种商品的全部消费，而必须补偿给他的货币量。CS = - p(x)x消费者剩余的变化：R测度的是消费者对继续消费的数量支付更多的货币而造成的损失；T测度的是因减少消费而造成的损失。生产者剩余： PS = np* - R；PS = p(x)x - ，生产者出售x单位实际得到的货币量和他愿意换取的最小货币量之间的差额。Market demand市场需求 Inverse demand curve：价格是数量的函数。度量的是当人们需求X单位的商品1时，对该商品必须支付的市场价格。是每个购买这种商品的消费者的边际替代率或边际支付意愿。The price elasticity of demand：销售数量的百分比变动除以价格百分比的变动。Elasticity and demandAn elastic demand（弹性需求）: | 1.An inelastic demand（无弹性需求）: | 1.Constant returns to scale（规模报酬不变）t f (x1, x2) = f (tx1, tx2).Increasing returns to scale（规模报酬递增）f (tx1, tx2) t f (x1, x2)Decreasing returns to scale（规模报酬递减）：f (tx1, tx2) =1的地方。由于一家垄断厂商索要的价格超过边际成本，所以会导致一个低效率的产量。低效率的程度可以用额外净损失（消费者剩余和生产者剩余的净损失）来度量。自然垄断：大量的固定成本和少量的边际成本并存。当一家厂商不可能在不亏损的情况下在一个有效率的产量水平上经营时，自然垄断就会出现。有效率的产量水平上经营时，自然垄断就会出现。许多公用事业单位就属于这类自然垄断厂商，因此，他们要由政府来管制。一个行业是竞争性行业还是垄断行业，部分地取决于技术的性质。如果最低效率规模相对于需求是大的，那么市场就有可能是垄断的。如果最低效率规模相对于需求是小的，行业中还存在供许多厂商活动的余地，那么，该行业就可能具有竞争性的市场结构。垄断行业中消费者的境况要差，垄断厂商的境况要好。垄断条件下存在“帕累托改进”。最低规模效率：相对于需求的水平，使平均成本实现最小化的产量水平。垄断竞争：利润为零，帕累托有效率。1. Each firm is selling at a price and output combination on its demand curve.2. Each firm is maximizing its profits.3. The profits of each firm is zero (in long-run).Factor Market 要素市场Marginal revenue product: (MRP，边际产品收益)=MRy MPx MRPx pMPx垄断情况下，边际产品收益总是小于边际产品价值。垄断厂商使用的要素总量比竞争厂商的更有价值，因为利润更大。但是在既定产量水平下，增加要素使用量会提高产量，降低垄断价格；而竞争厂商增加产量却不会改变价格；所以边际的产品价值，垄断厂商获得的要少于竞争厂商获得的价值。对此，垄断厂商通过使用较少的要素来提高利润。买方垄断：一个产品只有一个买主。假设：产品在竞争市场上出售；买方垄断厂商是价格制定者，面临的是向上的要素提供曲线。Oligopoly 寡头垄断Sequential game（序贯博弈）: the firms act at different time.Price leader（价格领导者）: the firm gets to set its price before the other firm.Price follower（价格追随者）: the firm set the price after price leader. Quantity leader（产量领导者）: the firm gets to choose its quantity first Quantity follower（产量追随者）: the firm chooses quantity after leader.寡头垄断的特征：市场上只有几家意识到它们的策略是互相依赖的厂商。寡头垄断厂商的行为有若干种可能的方式，这取决于它们相互影响的确切性质。斯塔克尔伯格产量领导模型：一家厂商先确定它的产量而处于领导者地位，另一家厂商则处于追随者地位。领导者在选择产量时，会考虑追随者将如何作出反应。价格领导模型：一家厂商制定它的价格，另一家厂商对按这个价格它将供给多少产量做出选择。再次地，领导者在进行决策的时候，必须考虑追随者的行为。Cournot model: two firms are simultaneously trying to decide what quantity to produce. 古诺模型：每家厂商在它对另一家厂商选择的预测既定的情况下，选择它的使自己的利润实现最大化产量。在均衡条件下，每家厂商都能发现它对另一家厂商的选择所作的预期得到了证实。每家厂商都只占有很小的市场份额，这意味着价格非常接近于边际成本也就是说，几乎是一个竞争的企业。Collusion：Firms can collude to get more profits- a cartel. Exchange 交换Partial equilibrium analysis: how demand and supply were affected by the price of the particular good we were examining. (局部均衡)General equilibrium analysis: how demand and supply conditions interact in several markets to determine the prices of many goods. (一般均衡) 一般均衡研究经济如何调节以使所有市场的需求同供给在同一时间内达成相等。The Edgeworth Box ：Two people: A and B.Two goods: 1 and 2. As consumption bundle: XA= (xA1, xA2)Bs consumption bundle: XB = (xB1, xB2). An allocation: (XA, XB).The initial endowment allocation, (wA1, wA2) and (wB1, w B 2).A feasible allocation (XA, XB):xA1 + xB1 = wA1 + wB1xA2 + xB2 = wA2 + wB2 Make a rectangle:Height: w2A + w2BWidth: w1A + w1BEquilibrium: the state no body would like change. MRSA12 = MRSB12-Pareto efficient allocation.Contract curve(契约曲线): the set of all Pareto efficient points.Walras law: the value of aggregate excess demand is identically zero for all possible choices of prices.（瓦尔拉斯法则）-only 5 equations are independent. Relative Prices ：In a k-good and n-person general equilibrium model, there are nk+ k = (n+1)k variables. Walras law implies that there are only (n+1)k 1 independent equations N种商品的价格对应于N-1种独立价格。First Theorem of Welfare Economics: all market equilibria are Pareto efficient.Second Theorem of Welfare Economics: if all agents have convex preferences, then there will always be a set of prices such that Pareto efficient allocation is a market equilibrium for an appropriate assignment of endowments.Production 生产Robinson Crusoe economy: economic model with one consumer, one firm, and two goods.Robinson Crusoe plays a dual role: both a consumer and a producer. Two goods: coconuts and leisure.Production and the First Welfare Theorem If all firms act as competitive profit maximizers, then a competitive equilibrium will be Pareto efficient.Production and the Second Welfare Theorem Any Pareto efficient allocation can be achieved through the use of competitive markets. Production possibilities set: the set of output goods that is feasible.Production possibilities frontier（生产可能性边界）: the boundary of production possibilities set.MRS = MRTThe equilibrium: the marginal rate of substitute of each consumer equals the marginal rate of transformation.MRSR = MRSF = MRT- necessary conditions for Pareto efficiency.Welfare 福利Utility possibilities set: the set of possible utilities in the case of two individuals. Utility possibilities frontier: The boundary of utility possibilities set.1. Given any set of complete, reflexive, and transitive individual preferences, the resulted social preferences satisfy the same properties.2. If everybody prefers alternative x to alternative y, then the social preferences should ra