微观经济学讲义PPT5

Chapter5,Demand,LearningObjectives,RelatetheLawofDemandtotheCost-BenefitPrincipleDiscusshowindividualwantsaretranslatedintodemandExplaintheRationalSpendingRuleApplyittobuyersdecisionsRelatetheRationalSpendingRuletosubstitutionandincomeeffectsDiscusstherelationshipbetweentheindividualdemandcurveandthemarketdemandcurveDefineandcalculateconsumersurplus,FreeIceCreamOrIsIt?,CostsofagoodextendbeyondthemonetarycostsWaitinginlinePurchasingapermitParticipatinginalotteryFreeicecreamattractsomanyconsumersthatthetimespentwaitinginlineactsasthepriceofthegoodDemandcurvesrelatethequantitydemandedtoALLcosts,notjustmonetarycosts,LawofDemand,LawofDemandPeopledolessofwhattheywanttodoasthecostofdoingitrises,Cost-BenefitPrincipleatworkDosomethingifthemarginalbenefitsareatleastasgreatasthemarginalcostsAnincreaseinthemarketpriceapproachesourreservationpriceIfmarketpriceexceedsthereservationprice,buynomoreCostsincludeALLcostsmoney,time,reputationConsiderimplicitandexplicitcosts,LawofDemand,OriginsofDemand,ReservationpriceIndividualtastesandpreferencesdifferBiologicalneedsCulturalinfluencesPeerbehaviorIndividualdifferencesPerceivedqualityExpectedbenefitsTastesmaychangeovertimeMacaroniandcheeseSpinachNewgoodsgetincorporatedintopriorities,NeedsversusWants,SomegoodsarerequiredforsubsistenceTheseareneedsBeyondsubsistence,behaviorisdrivenbywantsKidneysorhamburgerOatmealortoasterpastriesWantsdependonpriceWaterinCaliforniaRegulationsorpricemechanismRegulationsarecumbersomeandexpensivePricechangesarefastandeffective,CaliforniaWaterShortages,Problem:Californiahasalargepopulationandrelativelylowannualrainfall,sosomearguethatwatershortagesareinevitableAnalysisNewMexicohaslessrainfallperpersonandfewershortagesCaliforniaswaterpriceislowLowpricediscouragescarefuluseRiceisgrownbecausewaterischeapWater-intensivehomelandscaping,WantsandDemand,UnlimitedwantsMorethings,betterqualitythingsServices,includingentertainmentandtravelLimitedresourcesMoney,income,andwealthTimeandenergyPrioritizewantsAllocateresourcesaccordinglyDemandthosethingsforwhichyouarewillingandabletopay,WantsandUtility,Utility:thesatisfactionpeoplederivefromconsumptionWell-being,happinessMeasuredindirectlySubjectiveObservableCannotbecomparedbetweenpeopleIndividualgoalistomaximizeutilityAllocateresourcesaccordingly,SarahsUtilityfromIceCream,SarahsMarginalUtilityfromIceCream,Marginalutility:theadditionalutilityfromconsumingonemore,LawofDiminishingMarginalUtilityTendencyforadditionalutilitygainedfromconsuminganadditionalunitofagoodtodecreaseasconsumptionincreasesbeyondsomepoint,DiminishingMarginalUtility,DiminishingMarginalUtility,MarginalutilitycanincreaseatlowlevelsofconsumptionFirstunitstimulatesyourdesireformoreFirstMP-3playerina5-personhouseholdFirstpotatochipEventuallymarginalutilitydeclinesContinueconsumingApplyCost-BenefitPrincipleConsumeanadditionalunitaslongasthemarginalutility(benefit)isgreaterthanthemarginalcost,SpendingonTwoGoods,AssumeafixedbudgetDecidehowmuchofeachgoodtobuyLawofDiminishingMarginalReturnsappliesAsyoubuymoreofasinglegood,itsmarginalutilitydecreasesWhenyoubuylessofthatgood,itsmarginalutilityincreases,MarginalUtility,MarginalUtility,BudgetAllocation,MaximizeutilitywhenthemarginalutilityperdollarspentisthesameforallgoodsNoMoneyLeftOntheTablePrincipleCurrentspendinghasmarginalutilityofadollarspentononegoodhigherthanthemarginalutilityofadollarspentontheothergoodTakeadollarawayfromthegoodwithlowmarginalutilityandspenditonthegoodwithhighmarginalutilityMarginalutilitiesperdollarbegintoequalize,SarahsIceCream,$400budgetChocolateis$2perpintVanillais$1perpint,Buy200pintsofvanillaand100pintsofchocolateMarginalutilityis12forvanilla,16forchocolate,Pints/yr,VanillaIceCream,12,200,MU(utils/pint),SarahsNextStep,Increasevanillaby100Reducechocolateby50,Marginalutilityofvanillais8Marginalutilityofchocolateis24,SarahsEquilibrium,Optimalcombination:highesttotalutility250pintsvanilla;75pintschocolate,Marginalutility/priceisthesameforallgoodsMarginalutilityofvanilla10,chocolate20,SarahsChoices,TheRationalSpendingRuleSpendingshouldbeallocatedacrossgoodssothatthemarginalutilityperdollaristhesameforeachgood,RationalSpendingRule,RationalSpendingRule,RationalSpendingRulecanbewrittenalgebraicallyNotationMUCisthemarginalutilityfromchocolateMUVisthemarginalutilityfromvanillaPCisthepriceofchocolatePVisthepriceofvanillaRationalSpendingRuleMUC/PC=MUV/PVThemarginalutilityperdollarspentonchocolateequalsthemarginalutilityperdollarspentonvanilla,SubstitutionEffect,Whenthepriceofagoodgoesup,substitutesforthatgoodarerelativelymoreattractiveAtthehigherpricelessisdemandedbecausesomebuyersswitchtothesubstitutegoodIfthepriceofvanillaicecreamgoesup,somebuyerswillbuylessvanillaandmorechocolate,IncomeEffect,ChangesinpriceaffectthebuyerspurchasingpowerActslikeachangeinincomeSupposevanillaicecreamgoesfrom$1perpintto$2IfSarahspendsallherincomeonvanilla,theamountshecanbuygoesdownbyhalfAttheoriginalprices,shecouldbuy100pintsofvanillaand150pintsofchocolateAtnewpriceforvanilla,shebuys100vanillaandonly100chocolate,RationalSpendingandPriceChanges,Supposepriceofvanillaincreasesfrom$1to$2AttheoriginalequilibriumMUC/PC=MUV/PVWiththeincreaseinPV,MUV/PVMUC/PCIfSarahbuysmorechocolate,MUCwillgodownIfSarahbuyslessvanilla,MUVwillgoupTogettoanewoptimalspendingpoint,BuymorechocolateBuylessvanillaStopwhenmarginalutilityperdollaristhesame,EricsApples,IsEricfollowingtheRationalSpendingRule?,ApplyingtheRationalSpendingRule,SubstitutionhaspowerfuleffectsonourchoicesNewcarorusedoneCarpoolorbusFrenchrestaurant,Chineserestaurant,cookathomeSoccergameorTVorreadabookGotomoviesorjoinNetflixorgetcableTVTurnontheheatorputonahoodie,Example:SmallerHomesinManhattan,Observation:WealthypeopleinSeattlehavelargerhomesthanwealthypeopleinManhattanSeattlehousestwicethesizeofManhattanhousesAnalysisHousingpricesarehigherinManhattanLandismoreexpensiveConstructioncostsarehigherNewYorkersbuylesshousingandspendmoreonothergoodssuchasvacationhomes,travel,restaurantmeals,andtheatertickets,NominalandRealPrices,Nominalprice:theabsolutepriceofagoodintermsofdollarsThepriceyouseeonagoodinastoreRealprice:thenominalpriceofagoodrelativetotheaveragedollarpriceofallothergoodsRealpricesareadjustedforinflation,Observation:Peoplebought4-cylindercarsinthe1970s,returningto6-and8-cylindercarsinthe1990sAnalysis1973gaspricewashigherinrealtermsthanin1999$1.40in1999boughtmoreothergoodsthan$0.38boughtin1973Withlowerrealgasprices,peopleboughtbiggercarsSUVmarketboomedinthe1990sHighgaspricesin2004reversedthetrendagain,Example:HowManyCylindersinYourCar?,IncomeDifferencesMatter,IncomeisoneofthedeterminantsofdemandFreegoodshavemoretakersinlowerincomeneighborhoodsthaninhigherincomeareasThewaittogetthefreegoodisthepriceWaitingtimesinlowerincomeareaswillbelongerLoweropportunitycostoftheresidentstimeStoresinhigherincomeareashavelowerwaitingtimestopayforpurchasesThehighervalueoftimecausesthesepeopletobewillingtopayformorestorestaff,IndividualandMarketDemandCurves,ThemarketdemandisthehorizontalsumofindividualdemandcurvesAteachpossibleprice,addupthenumberofunitsdemandedbyindividualstogetthemarketdemand,Smith,Jones,Market,IdenticalIndividualDemandCurves,InthespecialcasewhereallbuyersdemandexactlythesamequantityateachpriceMultiplytheindividualquantitydemandedbythenumberofbuyerstogetthemarketdemand,Market,Individual,ConsumerSurplus,ConsumerssurplusisthedifferencebetweenthebuyersreservationpriceandthemarketpriceWithmultiplebuyersFindtheconsumersurplusforeachbuyerAdduptheindividualsurpluses,ConsumerSurplusonaGraph,Whenaproductissoldinwholeunits,thedemandcurveisastair-stepfunctionManygoodsareindivisible:movieticketsandTVsIfthemarketsuppliedonlyoneunit,themaximumpricewouldbe$11Forthesecondunit,thepriceis$10,andsoonThelastbuyergetsnoconsumersurplus,D,Units/day,Marginalutility(utils/pint),1,2,3,4,5,6,7,8,9,10,11,12,2,4,6,8,10,12,VanillaIceCream,ConsumerSurplusonaGraph,Marketpriceis