微观经济学原理曼昆英文第七章ppt课件

Consumers,Producers,andtheEfficiencyofMarkets,Economics,PRINCIPLESOF,N.GregoryMankiw,7,Inthischapter,lookfortheanswerstothesequestions:,Whatisconsumersurplus?Howisitrelatedtothedemandcurve?Whatisproducersurplus?Howisitrelatedtothesupplycurve?Domarketsproduceadesirableallocationofresources?Orcouldthemarketoutcomebeimprovedupon?,1,.,2,WelfareEconomics,Recall,theallocationofresourcesrefersto:howmuchofeachgoodisproducedwhichproducersproduceitwhichconsumersconsumeitWelfareeconomicsstudieshowtheallocationofresourcesaffectseconomicwell-being.First,welookatthewell-beingofconsumers.,.,3,WillingnesstoPay(WTP),Abuyerswillingnesstopayforagoodisthemaximumamountthebuyerwillpayforthatgood.WTPmeasureshowmuchthebuyervaluesthegood.,Example:4buyersWTPforaniPod,.,4,WTPandtheDemandCurve,Q:IfpriceofiPodis$200,whowillbuyaniPod,andwhatisquantitydemanded?,A:Anthony&FleawillbuyaniPod,Chad&Johnwillnot.Hence,Qd=2whenP=$200.,.,5,WTPandtheDemandCurve,Derivethedemandschedule:,4,John,Chad,Anthony,Flea,0125,3,Chad,Anthony,Flea,126175,2,Anthony,Flea,176250,1,Flea,251300,0,nobody,$301&up,Qd,whobuys,P(priceofiPod),.,6,WTPandtheDemandCurve,P,Q,.,7,AbouttheStaircaseShape,ThisDcurvelookslikeastaircasewith4stepsoneperbuyer.,P,Q,Iftherewereahuge#ofbuyers,asinacompetitivemarket,therewouldbeahuge#ofverytinysteps,anditwouldlookmorelikeasmoothcurve.,.,8,WTPandtheDemandCurve,AtanyQ,theheightoftheDcurveistheWTPofthemarginalbuyer,thebuyerwhowouldleavethemarketifPwereanyhigher.,P,Q,.,9,ConsumerSurplus(CS),Consumersurplusistheamountabuyeriswillingtopayminustheamountthebuyeractuallypays:CS=WTPP,SupposeP=$260.FleasCS=$300260=$40.TheothersgetnoCSbecausetheydonotbuyaniPodatthisprice.TotalCS=$40.,.,10,CSandtheDemandCurve,P,Q,P=$260FleasCS=$300260=$40TotalCS=$40,.,11,CSandtheDemandCurve,P,Q,Instead,supposeP=$220FleasCS=$300220=$80AnthonysCS=$250220=$30TotalCS=$110,.,12,CSandtheDemandCurve,P,Q,Thelesson:TotalCSequalstheareaunderthedemandcurveabovetheprice,from0toQ.,.,13,CSwithLotsofBuyers&aSmoothDCurve,Thedemandforshoes,AtQ=5(thousand),themarginalbuyeriswillingtopay$50forpairofshoes.SupposeP=$30.Thenhisconsumersurplus=$20.,.,14,CSwithLotsofBuyers&aSmoothDCurve,Thedemandforshoes,CSistheareab/wPandtheDcurve,from0toQ.Recall:areaofatriangleequalsxbasexheightHeight=$6030=$30.So,CS=x15x$30=$225.,$,.,15,HowaHigherPriceReducesCS,IfPrisesto$40,CS=x10 x$20=$100.TworeasonsforthefallinCS.,16,P,Q,demandcurve,A.FindmarginalbuyersWTPatQ=10.B.FindCSforP=$30.,SupposePfallsto$20.HowmuchwillCSincreasedueto,C.buyersenteringthemarketD.existingbuyerspayinglowerprice,$,ACTIVELEARNING1Consumersurplus,.,17,CostandtheSupplyCurve,Asellerwillproduceandsellthegood/serviceonlyifthepriceexceedshisorhercost.Hence,costisameasureofwillingnesstosell.,Costisthevalueofeverythingasellermustgiveuptoproduceagood(i.e.,opportunitycost).Includescostofallresourcesusedtoproducegood,includingvalueofthesellerstime.Example:Costsof3sellersinthelawn-cuttingbusiness.,.,18,CostandtheSupplyCurve,3,35&up,2,2034,1,1019,0,$09,Qs,P,Derivethesupplyschedulefromthecostdata:,.,19,CostandtheSupplyCurve,.,20,CostandtheSupplyCurve,P,Q,AteachQ,theheightoftheScurveisthecostofthemarginalseller,thesellerwhowouldleavethemarketifthepricewereanylower.,.,21,ProducerSurplus,P,Q,Producersurplus(PS):theamountasellerispaidforagoodminusthesellerscost,PS=Pcost,.,22,ProducerSurplusandtheSCurve,P,Q,PS=Pcost,SupposeP=$25.JacksPS=$15JanetsPS=$5ChrissysPS=$0TotalPS=$20,TotalPSequalstheareaabovethesupplycurveundertheprice,from0toQ.,.,23,PSwithLotsofSellers&aSmoothSCurve,Thesupplyofshoes,SupposeP=$40.AtQ=15(thousand),themarginalsellerscostis$30,andherproducersurplusis$10.,.,24,PSwithLotsofSellers&aSmoothSCurve,Thesupplyofshoes,PSistheareab/wPandtheScurve,from0toQ.Theheightofthistriangleis$4015=$25.So,PS=xbxh=x25x$25=$312.50,.,25,HowaLowerPriceReducesPS,IfPfallsto$30,PS=x15x$15=$112.50TworeasonsforthefallinPS.,P,Q,supplycurve,A.FindmarginalsellerscostatQ=10.B.FindtotalPSforP=$20.,SupposePrisesto$30.FindtheincreaseinPSdueto,C.selling5additionalunitsD.gettingahigherpriceontheinitial10units,26,ACTIVELEARNING2Producersurplus,.,27,CS,PS,andTotalSurplus,CS=(valuetobuyers)(amountpaidbybuyers)=buyersgainsfromparticipatinginthemarketPS=(amountreceivedbysellers)(costtosellers)=sellersgainsfromparticipatinginthemarketTotalsurplus=CS+PS=totalgainsfromtradeinamarket=(valuetobuyers)(costtosellers),.,28,TheMarketsAllocationofResources,Inamarketeconomy,theallocationofresourcesisdecentralized,determinedbytheinteractionsofmanyself-interestedbuyersandsellers.Isthemarketsallocationofresourcesdesirable?Orwouldadifferentallocationofresourcesmakesocietybetteroff?Toanswerthis,weusetotalsurplusasameasureofsocietyswell-being,andweconsiderwhetherthemarketsallocationisefficient.(Policymakersalsocareaboutequality,thougharefocushereisonefficiency.),.,29,Efficiency,Anallocationofresourcesisefficientifitmaximizestotalsurplus.Efficiencymeans:Thegoodsareconsumedbythebuyerswhovaluethemmosthighly.Thegoodsareproducedbytheproducerswiththelowestcosts.Raisingorloweringthequantityofagoodwouldnotincreasetotalsurplus.,.,30,EvaluatingtheMarketEquilibrium,Marketeqm:P=$30Q=15,000Totalsurplus=CS+PSIsthemarketeqmefficient?,.,31,WhichBuyersConsumetheGood?,EverybuyerwhoseWTPis$30willbuy.EverybuyerwhoseWTPis$30willnot.So,thesellerswiththelowestcostproducethegood.,.,33,DoesEqmQMaximizeTotalSurplus?,AtQ=20,costofproducingthemarginalunitis$35valuetoconsumersofthemarginalunitisonly$20Hence,canincreasetotalsurplusbyreducingQ.ThisistrueatanyQgreaterthan15.,.,34,DoesEqmQMaximizeTotalSurplus?,AtQ=10,costofproducingthemarginalunitis$25valuetoconsumersofthemarginalunitis$40Hence,canincreasetotalsurplusbyincreasingQ.ThisistrueatanyQlessthan15.,.,35,DoesEqmQMaximizeTotalSurplus?,Themarketeqmquantitymaximizestotalsurplus:Atanyotherquantity,canincreasetotalsurplusbymovingtowardthemarketeqmquantity.,.,36,AdamSmithandtheInvisibleHand,“Manhasalmostconstantoccasionforthehelpofhisbrethren,anditisvainforhimtoexpectitfromtheirbenevolenceonly.,AdamSmith,1723-1790,PassagesfromTheWealthofNations,1776,Hewillbemorelikelytoprevailifhecaninteresttheirself-loveinhisfavor,andshowthemthatitisfortheirownadvantagetodoforhimwhatherequiresofthem,Itisnotfromthebenevolenceofthebutcher,thebrewer,orthebakerthatweexpectourdinner,butfromtheirregardtotheirowninterest.,.,37,AdamSmithandtheInvisibleHand,“Everyindividualneitherintendstopromotethepublicinterest,norknowshowmuchheispromotingit.,AdamSmith,1723-1790,PassagesfromTheWealthofNations,1776,Heintendsonlyhisowngain,andheisinthis,asinmanyothercases,ledbyaninvisiblehandtopromoteanendwhichwasnopartofhisintention.,Norisitalwaystheworseforthesocietythatitwasnopartofit.Bypursuinghisowninteresthefrequentlypromotesthatofthesocietymoreeffectuallythanwhenhereallyintendstopromoteit.”,aninvisiblehand,.,38,TheFreeMarketvs.GovtIntervention,Themarketequilibriumisefficient.Nootheroutcomeachieveshighertotalsurplus.Govtcannotraisetotalsurplusbychangingthemarketsallocationofresources.Laissezfaire(Frenchfor“allowthemtodo”):thenotionthatgovtshouldnotinterferewiththemarket.,.,39,Thefreemarketvs.centralplanning,Supposeresourceswereallocatednotbythemarket,butbyacentralplannerwhocaresaboutsocietyswell-being.Toallocateresourcesefficientlyandmaximizetotalsurplus,theplannerwouldneedtoknoweverysellerscostandeverybuyersWTPforeverygoodintheentireeconomy.Thisisimpossible,andwhycentrally-plannedeconomiesareneververyefficient.,.,40,CONCLUSION,ThischapterusedwelfareeconomicstodemonstrateoneoftheTenPrinciples:Marketsareusuallyagoodwaytoorganizeeconomicactivity.Importantnote:Wederivedtheselessonsassumingperfectlycompetitivemarkets.Inotherconditionswewillstudyinlaterchapters,themarketmayfailtoallocateresourcesefficiently,.,41,CONCLUSION,Suchmarketfailuresoccurwhen:abuyerorsellerhasmarketpowertheabilitytoaffectthemarketprice.transactionshavesideeffects,calledexternalities,thataffectbystanders.(example:pollution)Wellusewelfareeconomicstoseehowpublicpolicymayimproveonthemarketoutcomeinsuchcases.Despitethepossibilityofmarketfailure,theanalysisinthischapterappliesinmanymarkets,andtheinvis