迈克尔版本微观经济学第十一章Chapter11SM.ppt

DecisionTimeFrames,Thefirmmakesmanydecisionstoachieveitsmainobjective:profitmaximization.Alldecisionscanbeplacedintwotimeframes:TheshortrunThelongrun,TheShortRunTheshortrunisatimeframeinwhichthequantityofoneormoreresourcesusedinproductionisfixed.Formostfirms,thecapital,calledthefirmsplant,isfixedintheshortrun.Otherresourcesusedbythefirm(suchaslabor,rawmaterials,andenergy)canbechangedintheshortrun.Theshortrunisthereforecharacterizedbylessflexibilityandfreedomtochoosethequantityofallinputs.,DecisionTimeFrames,TheLongRunThelongrunisatimeframeinwhichthequantitiesofallresourcesincludingtheplantsizecanbevaried.Thelongrunisthereforecharacterizedbymoreflexibilityandfreedomtochoosethequantityofallinputs.,DecisionTimeFrames,DecisionTimeFrames,Asunkcostisacostincurredbythefirmandcannotbechanged.Ifafirmsplanthasnoresalevalue,theamountpaidforitisasunkcost.Sunkcostsareirrelevanttoafirmscurrentdecisions.,Short-RunTechnologyConstraint,Technologyreferstotherelationshipbetweeninputsandoutput.Toincreaseoutputintheshortrun,afirmmustincreasetheamountofinputsemployed.Threeconceptsdescribetherelationshipbetweenoutputandthequantityoflaboremployed:1.Totalproduct2.Marginalproduct3.Averageproduct,ProductSchedulesTotalproductisthetotaloutputproducedinagivenperiod.Themarginalproductoflabouristhechangeintotalproductthatresultsfromaone-unitincreaseinthequantityoflabouremployed,withallotherinputsremainingthesame.Theaverageproductoflabourisequaltototalproductdividedbythequantityoflabouremployed.,Short-RunTechnologyConstraint,Table11.1showsafirmsproductschedules.Asthequantityoflabouremployedincreases:Totalproductincreases.Marginalproductincreasesinitiallybuteventuallydecreases.Averageproductincreasesinitiallybuteventuallydecreases.,Short-RunTechnologyConstraint,ProductCurvesProductcurvesaregraphsofthethreeproductconceptsthatshowhowtotalproduct,marginalproduct,andaverageproductchangeasthequantityoflabouremployedchanges.,Short-RunTechnologyConstraint,TotalProductCurveFigure11.1showsatotalproductcurve.Thetotalproductcurveshowshowtotalproductchangeswiththequantityoflabouremployed.,Short-RunTechnologyConstraint,ThetotalproductcurveissimilartothePPF.Itseparatesattainableoutputlevelsfromunattainableoutputlevelsintheshortrun.,Short-RunTechnologyConstraint,MarginalProductCurveFigure11.2showsthemarginalproductoflabourcurveandhowthemarginalproductcurverelatestothetotalproductcurve.Thefirstworkerhiredproduces4unitsofoutput.,Short-RunTechnologyConstraint,Thesecondworkerhiredproduces6unitsofoutputandtotalproductbecomes10units.,Thethirdworkerhiredproduces3unitsofoutputandtotalproductbecomes13units.,Andsoon.,Short-RunTechnologyConstraint,Theheightofeachbarmeasuresthemarginalproductoflabour.Forexample,whenlabourincreasesfrom2to3,totalproductincreasesfrom10to13,sothemarginalproductofthethirdworkeris3unitsofoutput.,Short-RunTechnologyConstraint,Tomakeagraphofthemarginalproductoflabour,wecanstackthebarsinthepreviousgraphsidebyside.,Themarginalproductoflabourcurvepassesthroughthemid-pointsofthesebars.,Short-RunTechnologyConstraint,Almostallproductionprocessesareliketheoneshownhereandhave:IncreasingmarginalreturnsinitiallyDiminishingmarginalreturnseventually,Short-RunTechnologyConstraint,IncreasingMarginalReturnsInitiallyWhenthemarginalproductofaworkerexceedsthemarginalproductofthepreviousworker,themarginalproductoflabourincreasesandthefirmexperiencesincreasingmarginalreturns.,Short-RunTechnologyConstraint,DiminishingMarginalReturnsEventuallyWhenthemarginalproductofaworkerislessthanthemarginalproductofthepreviousworker,themarginalproductoflabourdecreases.Thefirmexperiencesdiminishingmarginalreturns.,Short-RunTechnologyConstraint,Increasingmarginalreturnsarisefromincreasedspecializationanddivisionoflabour.Diminishingmarginalreturnsarisesfromthefactthatemployingadditionalunitsoflabourmeanseachworkerhaslessaccesstocapitalandlessspaceinwhichtowork.Diminishingmarginalreturnsaresopervasivethattheyareelevatedtothestatusofa“law.”Thelawofdiminishingreturnsstatesthat:Asafirmusesmoreofavariableinputwithagivenquantityoffixedinputs,themarginalproductofthevariableinputeventuallydiminishes.,Short-RunTechnologyConstraint,AverageProductCurveFigure11.3showstheaverageproductcurveanditsrelationshipwiththemarginalproductcurve.,Short-RunTechnologyConstraint,Whenmarginalproductexceedsaverageproduct,averageproductincreases.Whenmarginalproductisbelowaverageproduct,averageproductdecreases.Whenmarginalproductequalsaverageproduct,averageproductisatitsmaximum.,Short-RunTechnologyConstraint,Short-RunCost,Toproducemoreoutputintheshortrun,thefirmmustemploymorelabour,whichmeansthatitmustincreaseitscosts.Wedescribethewayafirmscostschangeastotalproductchangesbyusingthreecostconceptsandthreetypesofcostcurve:TotalcostMarginalcostAveragecost,TotalCostAfirmstotalcost(TC)isthecostofallresourcesused.Totalfixedcost(TFC)isthecostofthefirmsfixedinputs.Fixedcostsdonotchangewithoutput.Totalvariablecost(TVC)isthecostofthefirmsvariableinputs.Variablecostsdochangewithoutput.Totalcostequalstotalfixedcostplustotalvariablecost.Thatis:TC=TFC+TVC,Short-RunCost,Figure11.4showsafirmstotalcostcurves.,Totalfixedcostisthesameateachoutputlevel.,Totalvariablecostincreasesasoutputincreases.,Totalcost,whichisthesumofTFCandTVCalsoincreasesasoutputincreases.,Short-RunCost,Thetotalvariablecostcurvegetsitsshapefromthetotalproductcurve.,NoticethattheTPcurvebecomessteeperatlowoutputlevelsandthenlesssteepathighoutputlevels.,Incontrast,theTVCcurvebecomeslesssteepatlowoutputlevelsandsteeperathighoutputlevels.,Short-RunCost,PuttheTFCcurvebackinthefigure,andaddTFCtoTVC,andyouvegottheTCcurve.,Short-RunCost,MarginalCostMarginalcost(MC)istheincreaseintotalcostthatresultsfromaone-unitincreaseintotalproduct.Overtheoutputrangewithincreasingmarginalreturns,marginalcostfallsasoutputincreases.Overtheoutputrangewithdiminishingmarginalreturns,marginalcostrisesasoutputincreases.,Short-RunCost,AverageCostAveragecostmeasurescanbederivedfromeachofthetotalcostmeasures:Averagefixedcost(AFC)istotalfixedcostperunitofoutput.Averagevariablecost(AVC)istotalvariablecostperunitofoutput.Averagetotalcost(ATC)istotalcostperunitofoutput.ATC=AFC+AVC.,Short-RunCost,Figure11.5showstheMC,AFC,AVC,andATCcurves.TheAFCcurveshowsthataveragefixedcostfallsasoutputincreases.,TheAVCcurveisU-shaped.Asoutputincreases,averagevariablecostfallstoaminimumandthenincreases.,Short-RunCost,TheATCcurveisalsoU-shaped.,TheMCcurveisveryspecial.,TheoutputsoverwhichAVCisfalling,MCisbelowAVC.,TheoutputsoverwhichAVCisrising,MCisaboveAVC.,TheoutputatwhichAVCisattheminimum,MCequalsAVC.,Short-RunCost,Similarly,theoutputsoverwhichATCisfalling,MCisbelowATC.,TheoutputsoverwhichATCisrising,MCisaboveATC.,AttheminimumATC,MCequalsATC.,Short-RunCost,WhytheAverageTotalCostCurveIsU-ShapedThecostcurvesarerelatedtoproductcurves.Whenlaborismoreproductive,averagecostsarelow.WhenfirmexperiencesincreasingreturnstolaborandAPcurveisincreasing,ATCisfalling.WhenAPreachesitsmaximum,ATCreachesitsminimumWhenfirmsstarttoexperiencediminishingreturnstolaborandAPfalls,ATCrises,Short-RunCost,CostCurvesandProductCurvesTherelationshipdescribedbetweenaverageproductandaveragetotalcostinpreviousslidealsoholdstrueformarginalproductandmarginalcostcurves:Whenmarginalproductisrising,marginalcostisfalling.MCisatitsminimumatthesameoutputlevelatwhichmarginalproductisatitsmaximum.Whenmarginalproductisfalling,marginalcostisrising,Short-RunCost,Figure11.6showstheserelationships.,Short-RunCost,ShiftsinCostCurvesThepositionofafirmscostcurvesdependontwofactors:TechnologyPricesoffactorsofproduction,Short-RunCost,TechnologyTechnologicalchangeinfluencesboththeproductivitycurvesandthecostcurves.Anincreaseinproductivityshiftstheaverageandmarginalproductcurvesupwardandtheaverageandmarginalcostcurvesdownward.Ifatechnologicaladvancebringsmorecapitalandlesslabourintouse,fixedcostsincreaseandvariablecostsdecrease.,Short-RunCost,PricesofFactorsofProductionAnincreaseinthepriceofafactorofproductionincreasescostsandshiftsthecostcurves.Anincreaseinafixedcostshiftsthetotalcost(TC)andaveragetotalcost(ATC)curvesupwardbutdoesnotshiftthemarginalcost(MC)curve.Anincreaseinavariablecostshiftsthetotalcost(TC),averagetotalcost(ATC),andmarginalcost(MC)curvesupward.,Short-RunCost,Long-RunCost,Inthelongrun,allinputsarevariableandallcostsarevariable.TheProductionFunctionThebehavioroflong-runcostdependsuponthefirmsproductionfunction.Thefirmsproductionfunctionistherelationshipbetweenthemaximumoutputattainableandthequantitiesofbothcapitalandlabour.,Long-RunCost,Table11.3showsafirmsproductionfunction.Asthesizeoftheplantincreases,theoutputthatagivenquantityoflabourcanproduceincreases.Butasthequantityoflabourincreases,diminishingreturnsoccurforeachplant.,DiminishingMarginalProductofCapitalThemarginalproductofcapitalistheincreaseinoutputresultingfromaone-unitincreaseintheamountofcapitalemployed,holdingconstanttheamountoflaboremployed.Afirmsproductionfunctionexhibitsdiminishingmarginalreturnstolabor(foragivenplant)aswellasdiminishingmarginalreturnstocapital(foragivenquantityoflabor).Foreachplant,diminishingmarginalproductoflaborcreatesasetofshortrun,U-shapedcostscurvesforMC,AVC,andATC.,Long-RunCost,Short-RunCostandLong-RunCostTheaveragecostofproducingagivenoutputvariesanddependsonthefirmsplant.Thelargertheplant,thegreateristheoutputatwhichATCisataminimum.Thefirmhas4differentplants:1,2,3,or4knittingmachines.Eachplanthasashort-runATCcurve.ThefirmcancomparetheATCforeachoutputatdifferentplants.,Long-RunCost,Long-RunCost,Long-RunCost,Long-RunCost,Long-RunCost,Thelong-runaveragecostcurveismadeupfromthelowestATCforeachoutputlevel.So,wewanttodecidewhichplanthasthelowestcostforproducingeachoutputlevel.Letsfindtheleast-costwayofproducingagivenoutputlevel.Supposethatthefirmwantstoproduce13sweatersaday.,Long-RunCost,Long-RunCost,Long-RunCost,Long-RunCost,Long-RunCost,Long-RunCost,Long-RunAverageCostCurveThelong-runaveragecostcurveistherelationshipbetweenthelowestattainableaveragetotalcostandoutputwhenbot