微观经济学 第7章成本分析

1、成本分析第7章成本的经济分析7.13短期 The short run: The period in which firms can adjust production only by changing variable factors such as materials and labor but cannot change fixed factors such as capital.4固定成本 Fixed costs are expenses that must be paid even if the firm produces zero output. A firms fixed cost

2、s, sometimes called “overhead” (企业一般管理费用) or “sunk costs” (沉没成本), must be paid even if the firm produces no output, and they will not change if output changes.5变动成本 The cost related to variable factors is called variable cost (变动成本，可变成本). Variable costs are those which vary as output changes. By def

3、inition, VC begins at zero when q is zero.6总成本是可达到的最小成本 Total cost represents the lowest total dollar expense needed to produce each level of output q. 说明：与生产函数的处理类似，总成本也是指给定产量时的最小成本，目的是为了让成本函数关系具有唯一性。7Totalcostin short run:in long run:TotalcostVariablecost=FixedcostVariablecost+8(1)(2)(3)(4)Quantit

4、yFixed costVariable costTotal cost=(2)+(3)qFC($)VC($)TC($)055055155308525555110355751304551051605551552106552252809边际成本 The concept of marginal cost is one of the most essential in microeconomics. Marginal cost (MC) denotes the extra or additional cost of producing 1 extra unit of output.10一个有空座位的航空

5、公司的飞机，额外增加一个旅客的成本是很低的。但是，在炎热的夏天，当所有的空调都开启时，增加一份电的使用的成本是非常高的。边际成本的计算11(1)(2)(3)OutputTotal costMarginal costQTC($)MC($)05518521103130416052103025203050利用变动成本计算边际成本12(1)(2)(3)OutputTotal costMarginal costQTC($)MC($)00130255375410551553025203050数学推导 为什么可以用变动成本来计算边际成本：13MC = TCq+1 TCq = (VCq+1FC) (VCqFC

6、)= VCq+1 VCq总成本和边际成本的关系1415平均成本Average cost(or unit cost)=total costoutput=TCq=ACAveragefixed cost=fixed costoutput=FCq= AFCAveragevariable cost=variable costoutput=VCq= AVC16总成本、固定成本和变动成本Total costVariable costFixed costQuantityCost平均成本和边际成本17QuantityAverage and marginal costMCACAVCAFC平均成本最小平均变动成本最

7、小平均成本与边际成本的关系成本产量边际成本平均成本平均成本最低点边际成本曲线自下而上穿越平均成本曲线的最低点。18平均成本边际成本成本产量边际成本平均成本16元2212元边际成本平均成本,平均成本曲线随着产量增加而向下。19平均成本AC, then AC is rising. If MC=AC, then AC is at its low point. If MCAVC, then AVC is rising. If MC=AVC, then AVC is at its low point. If MCAVC, then AVC is falling.24= AVCqMCAVCqq1AVCq+

8、1QuantityAC and MCAC25 2 4 6 8 10 12 14 16 18 20 1 2 3 4 5 6 7 8 9 10 产量 成本 总成本变动成本边际成本平均成本平均变动成本数值计算的例子固定成本斜率和边际成本的关系26Tangent lineTotal cost curve1 unit of outputMarginal costaaTCMCQ27产量与成本之间的联系 The cost curve for a firm depends very closely on the prices of inputs and the firms production functio

9、n. If you know factor prices and the production function, you can calculate the cost curve. 说明：一个企业对要素市场价格的影响可以忽略不计，因此，通常假定要素的价格给定。从生产数据和投入成本导出成本28(1)(2)(3)(4)(5)(6)Output(tons of wheat)Land(acres)Labor(workers)Rent($ per acre)Wage($ per worker)Total cost($)01005.555511065.55?210115.55110310155.5513

10、0410215.55160510315.55?610455.552808521029报酬递减和U形成本曲线In the short run:企业资源最优配置标准 企业资源最优配置标准企业资源最优配置标准：最后一单位资源用于各项用途时带来的收益相等。30用途1用途2用途N用途3总资源总资源等边际原理的解释31用途1用途2用途N用途3总资源总资源追加10万元+利润5万元追加10万元+利润8万元 5.万元8万元3万元移动10万元边际生产力递减定律减少10万元-利润5.万元减少10万元-利润8.万元 32等边际原理$1$1ABABMPMPPPThis gives you the marginal pr

11、oduct per dollar of output.33最小成本规则To a given output:Marginal product of input APrice of input A=Marginal product of input BPrice of input B=替代规则 If the price of one factor falls while all other factor prices remain the same, firms will profit by substituting the now-cheaper factor for all the other

12、 factors.34MP of LaborPrice of Labor=MP of CapitalPrice of Capital要素的收入短期成本与长期成本的关系成本产量长期平均成本1 亩地2 亩地4 亩地3 亩地1 亩地更有利2 亩地更有利3 亩地更有利4 亩地更有利35规模经济与规模不经济成本产量长期平均成本规模经济产量增加使得产品平均成本降低规模不经济产量增加使得产品平均成本增大36经济成本和企业会计7.238经济成本和会计成本 经济成本经济成本（economic cost）：投入生产的所有资源的机会成本。 会计成本（accounting cost）：按照会计规则计算的成本 在会计帐

13、面上显示出来的经济成本称为外显（显性）成本（explicit costs），在会计帐面上不能显示出来的经济成本称为内含（隐性）成本（implicit costs）。经济利润 经济成本 = 外显成本 + 内含成本 = 机会成本 经济利润经济利润 = 销售收益 经济成本 经济利润是计入了所有使用的资源代价后的纯收益。39 一个体饭馆业主使用自己的店面， 1年盈利3万元，这个3万元称之为会计利润。 若不开饭馆，在所有可选工作中最高可赚得2万元，人力的经济成本就是2万元。如果店面用于出租可以获得1.5万元租金，那么店面的经济成本就是1.5 万元。 考虑到经济成本后，这个个体饭馆业主的经济利润为0.5

14、万元。40收益表41(1) Net sales$250,000Less cost of goods sold:(2) Materials$50,000(3) Labor cost90,000(4) Miscellaneous operating costs10,000(5) Less overhead costs:(6) Selling and administrative costs15,000(7) Rent for building5,000(8) Depreciation15,000(9) Operating expenses$185,000185,000(10) Net operat

15、ing income$65,000收益表（续）42(10)Net operating income$65,000Less:(11) interest charges on equipment loan6,000(12) State and local taxes4,000(13)Net income before income taxes$55,000(14)Less: Corporation income taxes18,000(15)Net income (or profit) after taxes$37,000(16)Less: Dividends paid on common sto

16、ck15,000(17)Addition or retained earnings$22,00043折旧$10,000$10,000$10,000$10,000$10,000$10,000$10,000$10,000$10,000$10,000The depreciation is taken in annual accounting charges over the assets accounting lifetimedepreciation = the capital goods historical cost or purchase price.Depreciation = the an

17、nual cost of a capital input that a company actually owns itself.资产负债表44AssetsLiabilities and net worthLiabilitiesCurrent assets:Current liabilities: Cash$20,000 Accounts payable$20,000 Inventory80,000 Notes payable30,000Fixed assets:Long-term liabilities: Equipment150,000 Bonds payable100,000 Build

18、ings100,000 Net worthStockholders equity: Common stock200,000Total$350,000 Total$350,00045关于资产负债表 The income statement measures the flows into and out of the firm, while the balance sheet measures the stocks of assets and liabilities at the end of the accounting year. A balance sheet must always bal

19、ance:Total assets = total liabilities + net worth例子 Suppose total assets are down $40,000; liabilities remain unchanged. This means total net worth has decreased by $40,000, and should write net worth down from the previous $200,000 to only $160,000.46AssetsLiabilities and net worthLiabilities$40,00

20、0Net worthCommon stock $40,00047会计惯例 The most important assumption used in a balance sheet is that the value placed on almost every item reflects its historical cost . This differs from the economists concept of “value”.财务欺诈 For example, the inventory of hot-dog buns is valued at the price that was

21、paid for them. A newly purchased fixed asset is valued at its purchase price (this being the historical-cost convention). 正是因为两种可能的计价，为影响收益的会计欺诈提供机会。4849说明 “收益表”是描述一指定会计时间段中货币流入和流出企业的情况。 “资产负债表”是指在某一特定的会计时刻，企业的资产、负债和所有者权益状况。 总之，“收益表”是对一时段而言的，“资产负债表”是对一时点而言的。机会成本7.351机会成本 The opportunity cost (机会成本)

22、is the value of the good and service forgone (放弃). The opportunity cost includes all consequences (结果), whether they reflect explicit monetary transactions (货币交易) or not. 52The immediate dollar cost of going to a movie instead of reading your economics textbook is the price of the movie ticket.The o

23、pportunity cost also includes the possibility of gaining a better understanding of microeconomics and therefore becoming more successful in business.市场价格与机会成本 在一个良好运行的市场上，价格等于机会成本。53$25.02 (Market price)$25.01 (Opportunity cost)$24.98生产、成本理论和企业决策附录生产函数的数值例子 The production function is a constant-retu

24、rns-to-scale production function, a special case of the Cobb-Douglas production function.55Q = output;L = labor; A = land.100 2QLA563464906006927758463164485486327057752824004905646326922453464234905486002002823464004484901412002452823163466543210123456Constant returns to scaleLaborLand5734649060069

25、27758463164485486327057752824004905646326922453464234905486002002823464004484901412002452823163466543210123456Diminishing marginal product of laborLaborLand8264544842583464906006927758463164485486327057752824004905646326922453464234905486002002823464004484901412002452823163466543210123456Diminishing

26、 marginal product of landLaborLand52586777101593464906006927758463164485486327057752824004905646326922453464234905486002002823464004484901412002452823163466543210123456LaborLandABCDA、B、C和D点的产量相等。给定产量的最低要素成本组合60(1)(2)(3)(4)Input CombinationTotal cost Total costLaborLandPL=$2PL=$2LAPA=$3PA=$1A1620?B23

27、137C3212?D6115?881361等产量曲线3464906006927758463164485486327057752824004905646326922453464234905486002002823464004484901412002452823163466543210123456LaborLand62654321Land0123456LaborABCDqEqual-product curve or isoquantThere are an infinite number of equal-product contour lines (等值线) in the map.CAL替代率6

28、3654321Land0123456LaborABDqMACLNMN: AMPA=L MPLALMPMPLA等成本线64654321Land012345678LaborLabor price = $2, Land price = $3TC=$3TC=$6TC=$9TC=$12TC=$15TC=$18equal-cost Line: TCqPqPAALL替代率65654321Land012345678LaborTC=$3TC=$6TC=$9TC=$12TC=$15equal-cost Line: TCqPqPAALLALAPA=L PLALPPLA最低成本投入组合66654321Land012345678LaborTC=$3TC=$6TC=$9TC=$12ABCDALMPMPLAALPPLAALALPPMPMP最低成本条件67ALALPPMPMPAALLPMPPMP说明 等产量线方法一般用于企业的长期行为分析，因为对于长期来说，所有的生产要素都可以改变，所以可以在等产量线上进行选择。 对于短期分析而言，按惯例一般不使用等产量线分析方法。68小结 经济成本，短期和长期的成本划分； 边