迈克尔版本微观经济学十一ChapterSMPPT课件

DecisionTimeFrames Thefirmmakesmanydecisionstoachieveitsmainobjective profitmaximization Alldecisionscanbeplacedintwotimeframes TheshortrunThelongrun TheShortRunTheshortrunisatimeframeinwhichthequantityofoneormoreresourcesusedinproductionisfixed Formostfirms thecapital calledthefirm splant isfixedintheshortrun Otherresourcesusedbythefirm suchaslabor rawmaterials andenergy canbechangedintheshortrun Theshortrunisthereforecharacterizedbylessflexibilityandfreedomtochoosethequantityofallinputs DecisionTimeFrames TheLongRunThelongrunisatimeframeinwhichthequantitiesofallresources includingtheplantsize canbevaried Thelongrunisthereforecharacterizedbymoreflexibilityandfreedomtochoosethequantityofallinputs DecisionTimeFrames DecisionTimeFrames Asunkcostisacostincurredbythefirmandcannotbechanged Ifafirm splanthasnoresalevalue theamountpaidforitisasunkcost Sunkcostsareirrelevanttoafirm scurrentdecisions Short RunTechnologyConstraint Technologyreferstotherelationshipbetweeninputsandoutput Toincreaseoutputintheshortrun afirmmustincreasetheamountofinputsemployed Threeconceptsdescribetherelationshipbetweenoutputandthequantityoflaboremployed 1 Totalproduct2 Marginalproduct3 Averageproduct ProductSchedulesTotalproductisthetotaloutputproducedinagivenperiod Themarginalproductoflabouristhechangeintotalproductthatresultsfromaone unitincreaseinthequantityoflabouremployed withallotherinputsremainingthesame Theaverageproductoflabourisequaltototalproductdividedbythequantityoflabouremployed Short RunTechnologyConstraint Table11 1showsafirm sproductschedules 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 Wedescribethewayafirm scostschangeastotalproductchangesbyusingthreecostconceptsandthreetypesofcostcurve TotalcostMarginalcostAveragecost TotalCostAfirm stotalcost TC isthecostofallresourcesused Totalfixedcost TFC isthecostofthefirm sfixedinputs Fixedcostsdonotchangewithoutput Totalvariablecost TVC isthecostofthefirm svariableinputs Variablecostsdochangewithoutput Totalcostequalstotalfixedcostplustotalvariablecost Thatis TC TFC TVC Short RunCost Figure11 4showsafirm stotalcostcurves Totalfixedcostisthesameateachoutputlevel Totalvariablecostincreasesasoutputincreases Totalcost whichisthesumofTFCandTVCalsoincreasesasoutputincreases Short RunCost Thetotalvariablecostcurvegetsitsshapefromthetotalproductcurve NoticethattheTPcurvebecomessteeperatlowoutputlevelsandthenlesssteepathighoutputlevels Incontrast theTVCcurvebecomeslesssteepatlowoutputlevelsandsteeperathighoutputlevels Short RunCost PuttheTFCcurvebackinthefigure andaddTFCtoTVC andyou vegottheTCcurve 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 ShiftsinCostCurvesThepositionofafirm scostcurvesdependontwofactors 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 runcostdependsuponthefirm sproductionfunction Thefirm sproductionfunctionistherelationshipbetweenthemaximumoutputattainableandthequantitiesofbothcapitalandlabour Long RunCost Table11 3showsafirm sproductionfunction Asthesizeoftheplantincreases theoutputthatagivenquantityoflabourcanproduceincreases Butasthequantityoflabourincreases diminishingreturnsoccurforeachplant DiminishingMarginalProductofCapitalThemarginalproductofcapitalistheincreaseinoutputresultingfromaone unitincreaseintheamountofcapitalemployed holdingconstanttheamountoflaboremployed Afirm sproductionfunctionexhibitsdiminishingmarginalreturnstolabor foragivenplant aswellasdiminishingmarginalreturnstocapital foragivenquantityoflabor Foreachplant diminishingmarginalproductoflaborcreatesasetofshortrun U shapedcostscurvesforMC AVC andATC Long RunCost Short RunCostandLong RunCostTheaveragecostofproducingagivenoutputvariesanddependsonthefirm splant Thelargertheplant thegreateristheoutputatwhichATCisataminimum Thefirmhas4differentplants 1 2 3 or4knittingmachines Eachplanthasashort runATCcurve ThefirmcancomparetheATCforeachoutputatdifferentplants Long RunCost Long RunCost Long RunCost Long RunCost Long RunCost Thelong runaveragecostcurveismadeupfromthelowestATCforeachoutputlevel So wewanttodecidewhichplanthasthelowestcostforproducingeachoutputlevel Let sfindtheleast costwayofproducingagivenoutputlevel Supposethatthefirmwantstoproduce13sweatersaday Long RunCost Long RunCost Long RunCost Long RunCost Long RunCost Long RunCost Long RunAverageCostCurveThelong runaveragecostcurveistherelationshipbetweenthelowestattainableaveragetotalcostandoutputwhenboththep