微觀經(jīng)濟學(xué) Chapter 7 （更新版）

Chapter7

AnalysisofCosts

黃新飛

InternationalBusinessSchoolSun－YatSenUniversity2中國案例分析1：非典啊非典型經(jīng)濟學(xué)關(guān)于非典的問題：其一，口罩價格暴漲，但大眾對口罩的需求量仍然大增，這有違反需求定律嗎？其二，假設(shè)非典之前的口罩價格是1元，非典發(fā)生后漲價為10元，為什么會出現(xiàn)這樣的現(xiàn)象？也就是說，為什么口罩供應(yīng)商的庫存是以1元購進的，現(xiàn)在卻以10元出售？其三，如果政府受輿論影響而出臺行政命令禁止口罩供應(yīng)商漲價，會有什么結(jié)果？3 1 2 3 4 5 6 7 8 Marginalcosts Average Averagevariable Averagetotal Fixed Variable Total (MC) fixedcosts fixedcostscosts(ATC) costs costs costs (changein (AFC) (AVC) (ATC)Output (FC) (VC) (TC) totalcosts) FC/Output VC/Output AFC+AVC 4 50 50 100 12.50 12.50 25.00 10 5 50 60 110 10.00 12.00 22.00

10 50 100 150 5.00 10.00 15.00 6 11 50 106 156 4.54 9.64 14.18 17 50 150 200 2.94 8.82 11.76 7 18 50 157 207 2.78 8.72 11.50 21 50 182 232 2.38 8.67 11.05 23 50 200 250 2.17 8.70 10.87 10 24 50 210 260 2.08 8.75 10.83 28 50 250 300 1.79 8.93 10.72 15 29 50 265 315 1.72 9.14 10.86 32 50 350 400 1.56 10.94 12.504 4 50 50 100 12.50 12.50 25.00 10 5 50 60 110 10.00 12.00 22.00

10 50 100 150 5.00 10.00 15.00 6 11 50 106 156 4.54 9.64 14.18 17 50 150 200 2.94 8.82 11.76 7 18 ? 157 207 2.78 8.72 11.50 21 ? 182 232 2.38 8.67 11.05 23 ? 200 250 2.17 8.70 10.87 10 24 ? 210 260 2.08 8.75 10.83 28 ? 250 300 1.79 8.93 10.72 15 29 ? 265 315 1.72 9.14 10.86 32 ? 350 400 1.56 10.94 12.50 1 2 3 4 5 6 7 8 Marginalcosts Average Averagevariable Averagetotal Fixed Variable Total (MC) fixedcosts fixedcostscosts(ATC) costs costs costs (changein (AFC) (AVC) (ATC)Output (FC) (VC) (TC) totalcosts) FC/Output VC/Output AFC+AVCThefirstcolumnisthequantityofcarsyourfactorycanproduceinthousandsandthesecondcolumnsimplyrepresentsyourfirm’sfixedcosts.Thesefixedcostsaresometimescalled“overhead”or“sunkcosts”andfixedcostsarethosecoststhatdonotchangewiththelevelofoutput.

5 1 2 3 4 5 6 7 8 Marginalcosts Average Averagevariable Averagetotal Fixed Variable Total (MC) fixedcosts fixedcostscosts(ATC) costs costs costs (changein (AFC) (AVC) (ATC)Output (FC) (VC) (TC) totalcosts) FC/Output VC/Output AFC+AVC 4 50 50 100 12.50 12.50 25.00 10 5 50 60 110 10.00 12.00 22.00

10 50 100 150 5.00 10.00 15.00 6 11 50 106 156 4.54 9.64 14.18 17 50 150 200 2.94 8.82 11.76 7 18 ? 157 207 2.78 8.72 11.50 21 ? 182 232 2.38 8.67 11.05 23 ? 200 250 2.17 8.70 10.87 10 24 ? 210 260 2.08 8.75 10.83 28 ? 250 300 1.79 8.93 10.72 15 29 ? 265 315 1.72 9.14 10.86 32 ? 350 400 1.56 10.94 12.50Examplesofsuchfixedcostsincluderent,interestonthebondsyouissuedtogetmoneytobuildyourfactory,insurancepremiums,thesalariesoftopmanagement,andsoon.505050505050506 1 2 3 4 5 6 7 8 Marginalcosts Average Averagevariable Averagetotal Fixed Variable Total (MC) fixedcosts fixedcostscosts(ATC) costs costs costs (changein (AFC) (AVC) (ATC)Output (FC) (VC) (TC) totalcosts) FC/Output VC/Output AFC+AVC 4 50 50 100 12.50 12.50 25.00 10 5 50 60 110 10.00 12.00 22.00

10 50 100 150 5.00 10.00 15.00 6 11 50 106 156 4.54 9.64 14.18 17 50 150 200 2.94 8.82 11.76 7 18 50 157 207 2.78 8.72 11.50 21 50 182 232 2.38 8.67 11.05 23 50 200 ? 2.17 8.70 10.87 10 24 50 210 ? 2.08 8.75 10.83 28 50 250 ? 1.79 8.93 10.72 15 29 50 265 ? 1.72 9.14 10.86 32 50 350 ? 1.56 10.94 12.50Variablecostsaresimplythosecoststhatchangewiththelevelofoutput.Bydefinition,VCbeginsatzerowhenqiszero.250260300315400+=Rawmaterials,fuel,andwagesareallvariablecosts.Notethattotalcostissimplyvariablecostsplusfixedcosts.7Totalcostinshortrun:inlongrun:TotalcostVariablecost=FixedcostVariablecost+8 1 2 3 4 5 6 7 8 Marginalcosts Average Averagevariable Averagetotal Fixed Variable Total (MC) fixedcosts fixedcostscosts(ATC) costs costs costs (changein (AFC) (AVC) (ATC)Output (FC) (VC) (TC) totalcosts) FC/Output VC/Output AFC+AVC 4 50 50 100 12.50 12.50 25.00 10 5 50 60 110 10.00 12.00 22.00

10 50 100 150 5.00 10.00 15.00 6 11 50 106 156 4.54 9.64 14.18 17 50 150 200 2.94 8.82 11.76 ? 18 50 157 207 2.78 8.72 11.50 21 50 182 232 2.38 8.67 11.05 23 50 200 250 2.17 8.70 10.87 ? 24 50 210 260 2.08 8.75 10.83 28 50 250 300 1.79 8.93 10.72 ? 29 50 265 315 1.72 9.14 10.86 32 50 350 400 1.56 10.94 12.50Marginalutilityistheadditionalutilityaconsumergetsfromaone-unitincreaseinconsumption.Howwouldyoudefinemarginalcost?9MarginalcostTheconceptofmarginalcostisoneofthemostessentialinmicroeconomics.Marginalcost(MC)denotestheextraoradditionalcostofproducing1extraunitofoutput.10Foranairlineflyingplaneswithemptyseats,theaddedcostofanotherpassengerisquitelow.Butonahotsummerday,wheneveryone’sconditionersarerunning,theaddedelectricpowercomesatahighmarginalcost.11 1 2 3 4 5 6 7 8 Marginalcosts Average Averagevariable Averagetotal Fixed Variable Total (MC) fixedcosts fixedcostscosts(ATC) costs costs costs (changein (AFC) (AVC) (ATC)Output (FC) (VC) (TC) totalcosts) FC/Output VC/Output AFC+AVC 4 50 50 100 12.50 12.50 25.00 10 5 50 60 110 10.00 12.00 22.00

10 50 100 150 5.00 10.00 15.00 6 11 50 106 156 4.54 9.64 14.18 17 50 150 200 2.94 8.82 11.76 7 18 50 157 207 2.78 8.72 11.50 21 50 182 232 2.38 8.67 11.05 23 50 200 250 2.17 8.70 10.87 10 24 50 210 260 2.08 8.75 10.83 28 50 250 300 1.79 8.93 10.72 15 29 50 265 315 1.72 9.14 10.86 32 50 350 400 1.56 10.94 12.50fallriseMC=TCq－

TCq-1=(VCq＋FC)－

(VCq-1＋FC)=VCq－

VCq-112TotalCostandMarginalCostOutputTotalcostOutputMarginalcost13TheSupplyCurveAggregateandmarginalcost(dollars)QuantityAVCACMCThesupplycurveisthatportionofthemarginalcostcurveabovetheaveragevariablecostcurve.14中國案例分析2：中山大學(xué)校區(qū)調(diào)整2000年中山大學(xué)珠海校區(qū)正式招生，開啟了中國高等學(xué)府異地辦學(xué)的“中大模式”。2004年大學(xué)城建設(shè)正式完工，中大面臨著兩難選擇：要不選擇離廣州較近的東校區(qū)（已有土地）進行新的大樓建設(shè)和新生擴招，或者是繼續(xù)在已投資10億元的珠海校區(qū)完善教學(xué)設(shè)施和科研環(huán)境。但是……（此處省略一萬字）2006年IBS誕生了。請評論。15課堂測試在MP曲線向下傾斜的產(chǎn)量內(nèi)：A、MC曲線向下傾斜B、AFC曲線向上傾斜C、企業(yè)處于規(guī)模經(jīng)濟中D、總成本曲線向上傾斜16AveragecostAveragecost(orunitcost)=totalcostoutput=TCq=ACAveragefixedcost=fixedcostoutput=FCq=AFCAveragevariablecost=variablecostoutput=VCq=AVC17Aggregateandmarginalcost(dollars)QuantityAVCMCAFCATCqTheAFCcurveapproacheszerobecauseasafirm’soutputincreases,itspreadsitsfixedcostsoveralargernumberofunitssoaveragefixedcostsmustfall.Forthesamereason,theAVCcurvemustapproachtheATCcurveasoutputincreases.AFC,AVCAndACCurves18TheRelationofACandMCACq+1=ACq×q＋MCq+1q＋1=ACq×(q＋1)＋MCq+1－ACqq＋1=

ACq＋MCq+1－ACqq＋119ConclusionIfMC>AVC,thenAVCisrising.IfMC=AVC,thenAVCisatitslowpoint.IfMC<AVC,thenAVCisfalling.QuantityACandMC=

AVCq＋MCq+1－AVCqq＋1AVCq+1AVC20RelationbetweenSlopeandMarginalCostTangentlineTotalcostcurve1unitofoutputMarginalcosta21TheLinkbetweenProductionandCostsThecostcurveforafirmdependsverycloselyon①thepricesofinputsand②thefirm’sproductionfunction.Ifyouknowfactorpricesandtheproductionfunction,youcancalculatethecostcurve.22DiminishingReturnsandProduceUpward-SlopeMCLaborMarginalproductoflaborMarginalcostOutputABDABDMCACIntheshortrun:23課堂測試假設(shè)在短期內(nèi)勞動是唯一的可變投入，并且勞動價格是常數(shù)，你能根據(jù)平均產(chǎn)量曲線和邊際產(chǎn)量曲線的形狀解釋AVC曲線和MC曲線為什么成U型？24Least-CostRuleToagivenoutput:MarginalproductofinputAPriceofinputA=MarginalproductofinputBPriceofinputB=……25Thisgivesyouthemarginalproductperdollarofoutput.EquimarginalPrinciple26課堂測試已知生產(chǎn)函數(shù)為Y=25/8L3/8K5/8，生產(chǎn)要素L和K的價格分別為3和10。試求：（1）廠商的生產(chǎn)函數(shù)最優(yōu)組合

（2）如果資本的數(shù)量K=9時，廠商的短期成本函數(shù)

（3）廠商的長期成本函數(shù)27SubstitutionRuleIfthepriceofonefactorfallswhileallotherfactorpricesremainthesame,firmswillprofitbysubstitutingthenow-cheaperfactorforalltheotherfactors.MPofLaborPriceofLabor=MPofCapitalPriceofCapital28TheLongRunAverageCostCurveQuantityCostsperunitSATC7SATC6SATC5SATC4SATC3SATC2SATC1LATCThelongrunaveragecostcurveistheenvelopeoftheshortrunaveragecostcurves.CapitalinputsarefixedintheshortrunandthereisapointontheATCcurvewhereaveragecostisminimized.29TheLongRunAverageCostCurveQuantityCostsperunitSATC7SATC6SATC5SATC4SATC3SATC2SATC1LATCIfthenumberofpossibleplantsizesisverylarge,thelongrunaveragecostcurveapproximatesasmoothcurve.30課堂測試“一個廠商如果現(xiàn)在的產(chǎn)量水平處于這個產(chǎn)量水平的平均成本最低點，而這時長期平均成本處于上升階段，于是可得出結(jié)論：這時短期邊際成本大約短期平均成本”。你認為這句話對嗎？31Economicvs.AccountingProfitsLet’stalkabouthowaneconomistmeasuresafirm’scostsandprofitsversushowanaccountantmeasuresthem.Inthisregard,aneconomist–asopposedtoanaccountant–willalwayscountnotonlyexplicitcostsbutimplicitcostsaswell.32OpportunityCostsIncludesallconsequences,whethertheyreflectexplicitmonetarytransactionsornot.Theimmediatedollarcostofgoingtoamovieinsteadofreadingyoureconomicstextbookisthepriceofthemovieticket.Theopportunitycostalsoincludesthepossibilityofgainingabetterunderstandingofmacroeconomicsandthereforebecomingmoresuccessfulinbusiness.33Supposebothyouandyourspouseearnaftertaxsalariesof$45,000ayearassalesrepresentativesforahospitalequipmentdistributor,butyouwanttodobetter.Youborrow$20,000fromthebankat10%interest.Youkickinanother$30,000ofyourownsavingsthathadbeenearningyou$1,500annuallyininterestincomefromyourportfolioofbondinvestments.Youalsokickoutatenantinthestorefrontthatyouownwhowaspayingyou$800inrentpermonth.ACaseofOpportunityCosts34Yourownfinancialcapital $1,500Kickingoutyourtenant 7,200Aftertaxsalaries 90,000Total $98,700Accountingprofit $90,450Economicprofit -$8,250Category OpportunityCostYouEndUpBeingWorseOff生產(chǎn)、成本理論和企業(yè)決策附錄36生產(chǎn)函數(shù)的數(shù)值例子Q=1002LAQ=output;L=labor;A=land.Theproductionfunctionisaconstant-returns-to-scaleproductionfunction,aspecialcaseoftheCobb-Douglasproductionfunction.373464906006927758463164485486327057752824004905646326922453464234905486002002823464004484901412002452823163466543210123456ConstantreturnstoscaleLaborLand383464906006927758463164485486327057752824004905646326922453464234905486002002823464004484901412002452823163466543210123456DiminishingmarginalproductoflaborLaborLand82645448423934649060069277584631644854863