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1、Chapter 7 Analysis of Costs,黄新飞 International Business School SunYat Sen University,2,中国案例分析1：非典啊非典型经济学,关于非典的问题：其一，口罩价格暴涨，但大众对口罩的需求量仍然大增，这有违反需求定律吗？其二，假设非典之前的口罩价格是1元，非典发生后涨价为10元，为什么会出现这样的现象？也就是说，为什么口罩供应商的库存是以1元购进的，现在却以10元出售？其三，如果政府受舆论影响而出台行政命令禁止口罩供应商涨价，会有什么结果？,3,12345 678Marginal costsAverageAverage
2、variableAverage total Fixed Variable Total(MC)fixed costs fixed costs costs(ATC)costs costs costs(change in(AFC)(AVC)(ATC)Output(FC)(VC)(TC)total costs)FC/Output VC/Output AFC+AVC,450 5010012.5012.5025.0010 550 6011010.0012.0022.001050100150 5.0010.0015.00 61150106156 4.54 9.6414.181750150200 2.94 8
3、.8211.76 71850157207 2.78 8.7211.502150182232 2.38 8.6711.052350200250 2.17 8.7010.87102450210260 2.08 8.7510.832850250300 1.79 8.9310.72152950265315 1.72 9.1410.863250350400 1.5610.9412.50,4,450 5010012.5012.5025.0010 550 6011010.0012.0022.001050100150 5.0010.0015.00 611501061564.54 9.6414.18175015
4、02002.94 8.8211.76 718?1572072.78 8.7211.5021?1822322.38 8.6711.0523?2002502.17 8.7010.871024?2102602.08 8.7510.8328?2503001.79 8.9310.721529?2653151.72 9.1410.8632?3504001.5610.9412.50,12345 678Marginal costsAverageAverage variableAverage total Fixed Variable Total(MC)fixed costs fixed costs costs(
5、ATC)costs costs costs(change in(AFC)(AVC)(ATC)Output(FC)(VC)(TC)total costs)FC/Output VC/Output AFC+AVC,The first column is the quantity of cars your factory can produce in thousands and the second column simply represents your firms fixed costs.These fixed costs are sometimes called“overhead”or“sun
6、k costs”and fixed costs are those costs that do not change with the level of output.,5,12345 678Marginal costsAverageAverage variableAverage total Fixed Variable Total(MC)fixed costs fixed costs costs(ATC)costs costs costs(change in(AFC)(AVC)(ATC)Output(FC)(VC)(TC)total costs)FC/Output VC/Output AFC
7、+AVC,450 5010012.5012.5025.0010 550 6011010.0012.0022.001050100150 5.0010.0015.00 611501061564.54 9.6414.1817501502002.94 8.8211.76 718?1572072.78 8.7211.5021?1822322.38 8.6711.0523?2002502.17 8.7010.871024?2102602.08 8.7510.8328?2503001.79 8.9310.721529?2653151.72 9.1410.8632?3504001.5610.9412.50,E
8、xamples of such fixed costs include rent,interest on the bonds you issued to get money to build your factory,insurance premiums,the salaries of top management,and so on.,50505050505050,6,12345 678Marginal costsAverageAverage variableAverage total Fixed Variable Total(MC)fixed costs fixed costs costs
9、(ATC)costs costs costs(change in(AFC)(AVC)(ATC)Output(FC)(VC)(TC)total costs)FC/Output VC/Output AFC+AVC,450 50 10012.5012.5025.0010 550 60 11010.0012.0022.001050100 150 5.0010.0015.00 61150106 1564.54 9.6414.181750150 2002.94 8.8211.76 71850157 2072.78 8.7211.502150182 2322.38 8.6711.052350200?2.17
10、 8.7010.87102450210?2.08 8.7510.832850250?1.79 8.9310.72152950265?1.72 9.1410.863250350?1.5610.9412.50,Variable costs are simply those costs that change with the level of output.By definition,VC begins at zero when q is zero.,250260300315400,+=,Raw materials,fuel,and wages are all variable costs.Not
11、e that total cost is simply variable costs plus fixed costs.,7,Totalcost,in short run:,in long run:,Totalcost,Variablecost,=,8,12345 678Marginal costsAverageAverage variableAverage total Fixed Variable Total(MC)fixed costs fixed costs costs(ATC)costs costs costs(change in(AFC)(AVC)(ATC)Output(FC)(VC
12、)(TC)total costs)FC/Output VC/Output AFC+AVC,450 5010012.5012.5025.0010 550 6011010.0012.0022.001050100150 5.0010.0015.00 611501061564.54 9.6414.1817501502002.94 8.8211.76?18501572072.78 8.7211.5021501822322.38 8.6711.0523502002502.17 8.7010.87?24502102602.08 8.7510.8328502503001.79 8.9310.72?295026
13、53151.72 9.1410.8632503504001.5610.9412.50,Marginal utility is the additional utility a consumer gets from a one-unit increase in consumption.How would you define marginal cost?,9,Marginal cost,The concept of marginal cost is one of the most essential in microeconomics.Marginal cost(MC)denotes the e
14、xtra or additional cost of producing 1 extra unit of output.,10,For an airline flying planes with empty seats,the added cost of another passenger is quite low.,But on a hot summer day,when everyones conditioners are running,the added electric power comes at a high marginal cost.,11,12345 678Marginal
15、 costsAverageAverage variableAverage total Fixed Variable Total(MC)fixed costs fixed costs costs(ATC)costs costs costs(change in(AFC)(AVC)(ATC)Output(FC)(VC)(TC)total costs)FC/Output VC/Output AFC+AVC,450 5010012.5012.5025.0010 550 6011010.0012.0022.001050100150 5.0010.0015.00 611501061564.54 9.6414
16、.1817501502002.94 8.8211.76 718501572072.78 8.7211.5021501822322.38 8.6711.0523502002502.17 8.7010.871024502102602.08 8.7510.8328502503001.79 8.9310.721529502653151.72 9.1410.8632503504001.5610.9412.50,fall,rise,MC=TCq TCq-1,=(VCqFC)(VCq-1FC),=VCq VCq-1,12,Total Cost and Marginal Cost,Output,Total c
17、ost,Output,Marginal cost,13,The Supply Curve,Aggregate and marginal cost(dollars),Quantity,AVC,AC,MC,The supply curve is that portion of the marginal cost curve above the average variable cost curve.,14,中国案例分析2：中山大学校区调整,2000年中山大学珠海校区正式招生，开启了中国高等学府异地办学的“中大模式”。2004年大学城建设正式完工，中大面临着两难选择：要不选择离广州较近的东校区（已有
18、土地）进行新的大楼建设和新生扩招，或者是继续在已投资10亿元的珠海校区完善教学设施和科研环境。但是（此处省略一万字）2006年IBS诞生了。请评论。,15,课堂测试,在MP曲线向下倾斜的产量内：A、MC曲线向下倾斜 B、AFC曲线向上倾斜 C、企业处于规模经济中 D、总成本曲线向上倾斜,16,Average cost,Average cost(or unit cost),=,total cost,output,=,TC,q,=,AC,Averagefixed cost,=,fixed cost,output,=,FC,q,=,AFC,Averagevariable cost,=,variabl
19、e cost,output,=,VC,q,=,AVC,17,Aggregate and marginal cost(dollars),Quantity,q,The AFC curve approaches zero because as a firms output increases,it spreads its fixed costs over a larger number of units so average fixed costs must fall.For the same reason,the AVC curve must approach the ATC curve as o
20、utput increases.,AFC,AVC And AC Curves,18,The Relation of AC and MC,ACq+1,=,ACqqMCq+1,q1,=,ACq(q1)MCq+1ACq,q1,=ACq,MCq+1ACq,q1,19,Conclusion,If MCAVC,then AVC is rising.If MC=AVC,then AVC is at its low point.If MCAVC,then AVC is falling.,Quantity,AC and MC,AVC,20,Relation between Slope and Marginal
21、Cost,Tangent line,Total cost curve,1 unit of output,Marginal cost,a,21,The Link between Production and Costs,The cost curve for a firm depends very closely on the prices of inputs and the firms production function.If you know factor prices and the production function,you can calculate the cost curve
22、.,22,Diminishing Returns and Produce Upward-Slope MC,Labor,Marginal product of labor,Marginal cost,Output,A,B,D,A,B,D,MC,AC,In the short run:,23,课堂测试,假设在短期内劳动是唯一的可变投入，并且劳动价格是常数，你能根据平均产量曲线和边际产量曲线的形状解释AVC曲线和MC曲线为什么成U型？,24,Least-Cost Rule,To a given output:,Marginal product of input A,Price of input A,
23、=,Marginal product of input B,Price of input B,=,25,This gives you the marginal product per dollar of output.,Equimarginal Principle,26,课堂测试,已知生产函数为Y=25/8 L3/8K5/8，生产要素L和K的价格分别为3和10。试求：（1）厂商的生产函数最优组合（2）如果资本的数量K=9时，厂商的短期成本函数（3）厂商的长期成本函数,27,Substitution Rule,If the price of one factor falls while all
24、other factor prices remain the same,firms will profit by substituting the now-cheaper factor for all the other factors.,MP of Labor,Price of Labor,=,MP of Capital,Price of Capital,28,The Long Run Average Cost Curve,Quantity,Costs per unit,LATC,The long run average cost curve is the envelope of the s
25、hort run average cost curves.,Capital inputs are fixed in the short run and there is a point on the ATC curve where average cost is minimized.,29,The Long Run Average Cost Curve,Quantity,Costs per unit,LATC,If the number of possible plant sizes is very large,the long run average cost curve approxima
26、tes a smooth curve.,30,课堂测试,“一个厂商如果现在的产量水平处于这个产量水平的平均成本最低点，而这时长期平均成本处于上升阶段，于是可得出结论：这时短期边际成本大约短期平均成本”。你认为这句话对吗？,31,Economic vs.Accounting Profits,Lets talk about how an economist measures a firms costs and profits versus how an accountant measures them.In this regard,an economist as opposed to an acc
27、ountant will always count not only explicit costs but implicit costs as well.,32,Opportunity Costs,Includes all consequences,whether they reflect explicit monetary transactions or not.The immediate dollar cost of going to a movie instead of reading your economics textbook is the price of the movie t
28、icket.The opportunity cost also includes the possibility of gaining a better understanding of macroeconomics and therefore becoming more successful in business.,33,Suppose both you and your spouse earn after tax salaries of$45,000 a year as sales representatives for a hospital equipment distributor,
29、but you want to do better.You borrow$20,000 from the bank at 10%interest.You kick in another$30,000 of your own savings that had been earning you$1,500 annually in interest income from your portfolio of bond investments.You also kick out a tenant in the storefront that you own who was paying you$800
30、 in rent per month.,A Case of Opportunity Costs,34,Your own financial capital$1,500Kicking out your tenant 7,200After tax salaries 90,000Total$98,700Accounting profit$90,450Economic profit-$8,250,CategoryOpportunity Cost,You End Up Being Worse Off,生产、成本理论和企业决策,附录,36,生产函数的数值例子,Q=100 2LA,Q=output;L=la
31、bor;A=land.,The production function is a constant-returns-to-scale production function,a special case of the Cobb-Douglas production function.,37,Constant returns to scale,Labor,Land,38,Diminishing marginal product of labor,Labor,Land,39,Diminishing marginal product of land,Labor,Land,40,给定产量的最低要素成本
32、组合,41,给定产量的最低要素成本组合,42,等产量曲线,Labor,Land,43,Land,Labor,A,B,C,D,q,Equal-product curve or isoquant,There are an infinite number of equal-product contour lines(等值线)in the map.,44,Land,Labor,A,B,D,q,MN:AMPA=L MPL,替代率,45,等成本线,Land,Labor,Labor price=$2,Land price=$3,TC=$3,TC=$6,TC=$9,TC=$12,TC=$15,TC=$18,equal-cost Line:,46,Land,Labor,TC=$3,TC=$6,TC=$9,TC=$12,TC=$15,equal-cost Line:,APA=L PL,替代率,47,最低成本投入组合,Land,Labor,TC=$3,TC=$6,TC=$9,TC=$12,A,B,C,D,48,最低成本条件,EQUIMARGINAL PRINCIPLE,
