范里安微观第21章讲义.ppt

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1、ChapterTwenty-OneCostCurves成本曲线StructureTypesofcostcurvesFixed,variableandtotalcostfunctionsAveragefixed,averagevariableandaveragecostfunctionsMarginalcostfunctionsMarginalandvariablecostfunctionsMarginalandaveragecostfunctionsShortrunandlongruncostcurvesT

2、ypesofCostCurvesAtotalcostcurve（总成本曲线）isthegraphofafirm’stotalcostfunction.Avariablecostcurve（可变成本曲线）isthegraphofafirm’svariablecostfunction.Anaveragetotalcostcurve（平均成本曲线）isthegraphofafirm’saveragetotalcostfunction.TypesofCostCurvesAnaveragevariablecostcu

3、rve（平均可变成本曲线）isthegraphofafirm’saveragevariablecostfunction.Anaveragefixedcostcurve（平均固定成本曲线）isthegraphofafirm’saveragefixedcostfunction.Amarginalcostcurve（边际成本曲线）isthegraphofafirm’smarginalcostfunction.TypesofCostCurvesHowarethesecostcurvesrelatedtoeachot

4、her?Howareafirm’slong-runandshort-runcostcurvesrelated?Fixed,Variable&TotalCostFunctionsFisthetotalcosttoafirmofitsshort-runfixedinputs（固定投入）.F,thefirm’sfixedcost,doesnotvarywiththefirm’soutputlevel.cv(y)isthetotalcosttoafirmofitsvariableinputs（可变投入）whenpr

5、oducingyoutputunits.cv(y)isthefirm’svariablecostfunction.cv(y)dependsuponthelevelsofthefixedinputs.Fixed,Variable&TotalCostFunctionsc(y)isthetotalcostofallinputs,fixedandvariable,whenproducingyoutputunits.c(y)isthefirm’stotalcostfunction;y$Fy$cv(y)y$Fcv(y)

6、y$Fcv(y)c(y)FAv.Fixed,Av.Variable&Av.TotalCostCurvesThefirm’stotalcostfunctionisFory>0,thefirm’saveragetotalcostfunctionisAv.Fixed,Av.Variable&Av.TotalCostCurvesWhatdoesanaveragefixedcostcurvelooklike?AFC(y)isarectangularhyperbolasoitsgraphlookslike...$/

7、outputunitAFC(y)y0AFC(y)®0asy®¥Av.Fixed,Av.Variable&Av.TotalCostCurvesInashort-runwithafixedamountofatleastoneinput,theLawofDiminishing(Marginal)Returnsmustapply,causingthefirm’saveragevariablecostofproductiontoincreaseeventually.$/outputunitAVC(y)y0$/outp

8、utunitAFC(y)AVC(y)y0Av.Fixed,Av.Variable&Av.TotalCostCurvesAndATC(y)=AFC(y)+AVC(y)$/outputunitAFC(y)AVC(y)ATC(y)y0ATC(y)=AFC(y)+AVC(y)$/outputunitAFC(y)AVC(y)ATC(y)y0AFC(y)=ATC(y)-AVC(y)AFC$/outputunitAFC(y)A