ch03财货市场均衡凯因斯课件

ch03财货市场均衡凯因斯课件頭腦體操？為什麼會有失業？造成的原因是什麼？1930年代經濟大恐慌，為何有普遍失業的現象?失業產生究竟是因為企業生產萎縮(供給不足)所致，還是商品賣不出去(需求不足)所致?近一二年，全球及台灣普遍高失業率的現象，是供給面還是需求面所引起？台灣經濟不好，是那裡出了問題？中央要「拼經濟，救台灣」，如何拼法呢？過去台灣經濟不好時，政府總會提出振興投資方案、擴大內需政策---等，建立在什麼觀點上？你認為成效又如何？增加一元的投資支出或政府支出，可創造比一元還多的產出或所得，可能嗎？為何？決定家計消費支出的因素為何？決定企業投資的關鍵又如何？「節儉是美德」嗎？一經濟社會人們想增加儲蓄，是否整個經濟社會儲蓄水準就會增加？政府財政政策，如何能達到經濟穩定的目的？利用何種財政工具？國外經濟不景氣，台灣經濟跟著不好，如何說明這種現象？頭腦體操？為什麼會有失業？造成的原因是什麼？簡單凱因斯模型--理論基礎依據：凱因斯1936年「就業、利息與貨幣的一般理論」，1930年代經濟大恐慌提出。是需要面經濟學，主要說明失業為何產生及如何解決失業問題。當時勞動未充分就業，工資又無法向下調整，使企業缺乏增加勞動雇用的誘因。解決失業問題之法在提高總需求，貨暢其流，東西有銷路，生產增加，勞動需求自然增加。古典經濟學：是供給面經濟學，經由自由市場的價格機能，經濟常處於充分就業狀態，資本、技術、勞動供給量等生產能量決定總供給，總需求只影響物價水準而已。模式：依總合供需圖而言凱因斯學派—AS水平，產出與就業決定於總需求。古典學派—AS垂直，產出與就業決定於總供給，總需求只影響物價水準。中間區—AS正斜率，總需求與總供給共同決定產出、就業與物價。假定：物價不變，不計利率或金融(貨幣)面的作用(本章)主旨：民間消費、企業投資、政府支出、對外貿易如何影響一國所得3簡單凱因斯模型--理論基礎依據：凱因斯1936年「就業、利息3-1TheCompositionofGDPTable3-1TheCompositionofU.S.GDP,2006Billionsofdollars

PercentofGDPGDP(Y)13,246100.01Consumption(C)9,26970.02Investment(I)2,16316.3Nonresidential

1,39610.5Residential7675.83Governmentspending(G)2,52819.04Netexports7635.8

Exports(X)1,46611.0

Imports(IM)2,22916.85Inventoryinvestment490Source:SurveyofCurrentBusiness,April2007,Table1-1-5.43-1TheCompositionofGDPTab3-1TheCompositionofGDPConsumption(C)referstothegoodsandservicespurchasedbyconsumers.

Investment(I),sometimescalledfixedinvestment,isthepurchaseofcapitalgoods.Itisthesumofnonresidentialinvestmentandresidentialinvestment.

GovernmentSpending(G)referstothepurchasesofgoodsandservicesbythefederal,state,andlocalgovernments.Itdoesnotincludegovernmenttransfers,norinterestpaymentsonthegovernmentdebt.53-1TheCompositionofGDPCon3-1TheCompositionofGDPImports(IM)arethepurchasesofforeigngoodsandservicesbyconsumers,businessfirms,andtheU.S.government.

Exports(X)arethepurchasesofU.S.goodsandservicesbyforeigners.63-1TheCompositionofGDPImp3-1TheCompositionofGDPInventoryinvestmentisthedifferencebetweenproductionandsales.Netexports(XIM)isthedifferencebetweenexports

andimports,alsocalledthetradebalance.73-1TheCompositionofGDPInv3-2TheDemandforGoodsThetotaldemandforgoodsiswrittenas:Thesymbol“”meansthatthisequationisanidentity,ordefinition.TodetermineZ,somesimplificationsmustbemade:

Assumethatallfirmsproducethesamegood,whichcanthenbeusedbyconsumersforconsumption,byfirmsforinvestment,orbythegovernment.

83-2TheDemandforGoodsThet3-2TheDemandforGoodsAssumethatfirmsarewillingtosupplyanyamountofthegoodatagivenprice,P,anddemandinthatmarket.

Assumethattheeconomyisclosed,thatitdoesnottradewiththerestoftheworld,thenbothexportsandimports

arezero.Undertheassumptionthattheeconomyisclosed,

X=IM=0,then:93-2TheDemandforGoods93-2TheDemandforGoodsDisposableincome,(YD),istheincomethatremainsonceconsumershavepaidtaxesandreceivedtransfersfromthegovernment.ThefunctionC(YD)iscalledtheconsumptionfunction.Itisabehavioralequation,thatis,itcapturesthebehaviorofconsumers.Consumption(C)Amorespecificformoftheconsumptionfunctionisthislinearrelation:103-2TheDemandforGoodsDispo簡單凱因斯模型—民間消費與儲蓄影響消費支出的因素：可支配所得、利率、未來預期、資產或財富多寡、物價水準、貸款信用的條件與數量、所得分配狀況、家庭人口數與年齡結構。消費支出與可支配所得關係：凱恩斯提出消費基本心理法則(fundamentalpsychologicallaw)

所得增加消費支出增加；但消費額增量小於所得增量；且隨所得增加，平均消費額下降。消費函數：C＝co＋c1YD，Co是自發性消費、c1YD是誘發性消費，0＜c1＜1。消費傾向：邊際消費傾向(MPC)＝ΔC/ΔYD＝c

平均消費傾向(APC)＝C/YD＝(co/YD

)＋c1＞MPC儲蓄函數：S＝YD－C＝－co＋(1－c1)YD，

MPS＝ΔS/ΔYD，APS＝S/YD

消費傾向與儲蓄傾向關係：MPC＋MPS＝1，APC＋APS＝111簡單凱因斯模型—民間消費與儲蓄影響消費支出的因素：可支配所得可支配所得、消費、儲蓄

單位：萬元YCS△Y△C△SAPCAPSMPCMPC06-6-------1012-210641.2-20.60.4201821060.4302441060.440301010640.750361410640.720.280.60.460421810640.700.300.60.470482210640.690.310.60.412可支配所得、消費、儲蓄3-2TheDemandforGoodsThisfunctionhastwoparameters,c0andc1:

c1iscalledthe(marginal)propensitytoconsume,ortheeffectofanadditionaldollarofdisposableincomeonconsumption.

c0istheinterceptoftheconsumptionfunction. Disposableincomeisgivenby:Consumption(C)133-2TheDemandforGoodsThis3-2TheDemandforGoodsConsumption(C)Consumptionincreaseswithdisposableincomebutlessthanoneforone.ConsumptionandDisposableIncomeFigure3-1143-2TheDemandforGoodsConsu3-2TheDemandforGoodsVariablesthatdependonothervariableswithinthemodelarecalledendogenous.Variablesthatarenotexplainwithinthemodelarecalledexogenous.Investmenthereistakenasgiven,ortreatedasanexogenousvariable:

Investment(I)GovernmentSpending(G)Governmentspending,G,togetherwithtaxes,T,describesfiscalpolicy—thechoiceoftaxesandspendingbythegovernment.153-2TheDemandforGoodsVaria3-2TheDemandforGoods

WeshallassumethatGandTarealsoexogenousfortworeasons:

Governmentsdonotbehavewiththesameregularityasconsumersorfirms.

Macroeconomistsmustthinkabouttheimplicationsofalternativespendingandtaxdecisionsofthegovernment.163-2TheDemandforGoodsWes簡單凱因斯模型—投資支出定義：投資指新資本財的購買，資本財含機械設備、建築物(合稱固定資本)，及存貨變動。投資毛額＝投資淨額＋資本折舊，Kt＋1＝Kt＋It(投資毛額)－Dt＝Kt＋Int(投資淨額)影響投資需求因素：最適投資量決定於投資的邊際收益＝邊際成本成本方面—利率(投資的機會成本)下降、資本財價格下降，投資需求增加；反之，則減少。收益方面—產品未來銷售量或價格看好、技術改良或創新出現、資本設備利用率高、生產成本降低、稅捐減輕，投資需求增加；反之，則減少。

(政府公共投資有助於改善投資環境，而降低民間生產成本，提高民間投資意願；但擴大支出以發行大量公債支應，可能刺激利率上揚，不利民間投資。)投資函數：I＝I(i，Y)，i是利率，Y是所得17簡單凱因斯模型—投資支出定義：投資指新資本財的購買，資本財含3-3TheDeterminationofEquilibriumOutputAssumingthatexportsandimportsarebothzero,thedemandforgoodsisthesumofconsumption,investment,andgovernmentspending:Then:183-3TheDeterminationofEquiEquilibriuminthegoodsmarketrequiresthatproduction,Y,beequaltothedemandforgoods,Z:Then:Theequilibriumconditionisthat,production,Y,beequaltodemand.Demand,Z,inturndependsonincome,Y,whichitselfisequaltoproduction.3-3TheDeterminationofEquilibriumOutput19Equilibriuminthegoodsmarke3-3TheDeterminationofEquilibriumOutputMacroeconomistsalwaysusethesethreetools:AlgebratomakesurethatthelogiciscorrectGraphstobuildtheintuitionWordstoexplaintheresults203-3TheDeterminationofEqui3-3TheDeterminationofEquilibriumOutput

Rewritetheequilibriumequation:

UsingAlgebra

Movetotheleftsideandreorganizetherightside:

Dividebothsidesby213-3TheDeterminationofEquiTheequilibriumequationcanbemanipulatedtoderivesomeimportantterms:

Autonomousspendingandthemultiplier:Thetermisthatpartofthedemandforgoodsthatdoesnotdependonoutput,itiscalledautonomousspending.Ifthegovernmentranabalancedbudget,thenT=G.Becausethepropensitytoconsume(c1)isbetweenzeroandone,isanumbergreaterthanone.Forthisreason,thisnumberiscalledthemultiplier.3-3TheDeterminationofEquilibriumOutputUsingAlgebra22Theequilibriumequationcanb均衡所得決定—封閉經濟假定：不計國外部門，投資需求、政府支出外生決定，租稅為定額稅。均衡：Z=AE＝Y，預擬總支出(C+I+G消費支出、投資支出政府支出)與總產出或所得相等；Y＝1/(1－c1)×(co＋I0+G-c1T0)或原先打算進行的預擬(或事前)投資與預擬儲蓄相等，S＝I。(國民所得帳之C,S,I是事後或實際發生的數量，實現的儲蓄必恆等於實現的投資)如Z=AE＞Y或I＞S，表非意願存貨減少，企業增加生產，所得增加，直到Z=AE＝Y為止。如Z=AE＜Y或I＜S，表非意願存貨增加，企業減少生產，所得下降，直到Z=AE＝Y為止。23均衡所得決定—封閉經濟233-3TheDeterminationofEquilibriumOutputFirst,plotproductionasafunctionofincome.Second,plotdemandasafunctionofincome.InEquilibrium,productionequalsdemand.Equilibriumoutputisdeterminedbytheconditionthatproductionbeequaltodemand.EquilibriumintheGoodsMarketFigure3-2UsingaGraph243-3TheDeterminationofEquiUsingaGraphAnincreaseinautonomousspendinghasamorethanone-for-oneeffectonequilibriumoutput.TheEffectsofanIncreaseinAutonomousSpendingonOutputFigure3-33-3TheDeterminationofEquilibriumOutput25UsingaGraphAnincreaseinauUsingaGraphThefirst-roundincreaseindemand,shownbythedistanceABequals$1billion.Thisfirst-roundincreaseindemandleadstoanequalincreaseinproduction,or$1billion,whichisalsoshownbythedistanceinAB.Thisfirst-roundincreaseinproductionleadstoanequalincreaseinincome,shownbythedistanceinBC,alsoequalto$1billion.3-3TheDeterminationofEquilibriumOutput26UsingaGraphThefirst-roundiUsingaGraphThesecond-roundincreaseindemand,shownbythedistanceinCD,equals$1billiontimesthepropensitytoconsume.Thissecond-roundincreaseindemandleadstoanequalincreaseinproduction,alsoshownbythedistanceDC,andthusanequalincreaseinincome,shownbythedistanceDE.Thethird-roundincreaseindemandequals$c1billion,timesc1,themarginalpropensitytoconsume;itisequalto$c1

xc1

=$c12billion.3-3TheDeterminationofEquilibriumOutput27UsingaGraphThesecond-roundFollowingthislogic,thetotalincreaseinproductionafter,say,n+1

rounds,equals$1billionmultipliedbythesum:1+c1+c12+…+c1nSuchasumiscalledageometricseries.3-3TheDeterminationofEquilibriumOutputUsingaGraph28Followingthislogic,thetotaTosummarize:Anincreaseindemandleadstoanincreaseinproductionandacorrespondingincreaseinincome.Theendresultisanincreaseinoutputthatislargerthantheinitialshiftindemand,byafactorequaltothemultiplier.

Toestimatethevalueofthemultiplier,andmoregenerally,toestimatebehavioralequationsandtheirparameters,economistsuseeconometrics—asetofstatisticalmethodsusedineconomics.3-3TheDeterminationofEquilibriumOutputUsingWords29Tosummarize:3-3TheDeterminDescribingformallytheadjustmentofoutputovertimeiswhateconomistscallthedynamicsofadjustment.Supposethatfirmsmakedecisionsabouttheirproductionlevelsatthebeginningofeachquarter.Nowsupposeconsumersdecidetospendmore,thattheyincreasec0..Havingobservedanincreaseindemand,firmsarelikelytosetahigherlevelofproductioninthefollowingquarter.Inresponsetoanincreaseinconsumerspending,outputdoesnotjumptothenewequilibrium,butratherincreasesovertime.3-3TheDeterminationofEquilibriumOutputHowLongDoesItTakeforOutputtoAdjust?30DescribingformallytheadjustConsumerConfidenceandthe1990to1991RecessionAforecasterroristhedifferencebetweentheactualvalueofGDPandthevaluethathadbeenforecastbyeconomistsonequarterearlier.

Theconsumerconfidenceindexiscomputedfromamonthlysurveyofabout5,000householdswhoareaskedhowconfidenttheyareaboutbothcurrentandfutureeconomicconditions.31ConsumerConfidenceandthe19均衡所得變動—民間部門乘數：自發支出(所得以外的因素引起)變動會使均衡所得呈倍數變動，稱為乘數效果。

ΔY＝ΔAEo×1/(1－c1)，乘數＝1/(1－c1)，邊際消費傾向越大，乘數效果越大。引申：節儉矛盾(paradoxofthrift)大眾自發性儲蓄意願增加，結果整個社會儲蓄水準並未增加。因為大眾增加自發性儲蓄(自發性消費減少)，使均衡所得下降，誘發性儲蓄隨之減少，抵消了自發儲蓄。(如投資是所得的增函數，均衡所得下降後，均衡時的投資與儲蓄則下降)是依據凱因斯模型的結論：為需要面或支出面理論，及失業情況下。如依古典理論或經濟處於充分就業下，節儉矛盾會產生嗎？32均衡所得變動—民間部門乘數：自發支出(所得以外的因素引起)變ConsumerConfidenceandthe1990to1991RecessionTable1GDP,Consumption,andForecastErrors,1990-1991Quarter(1)Change

inRealGDP(2)Forecast

ErrorforGDP

(3)Forecast

Errorforc0(4)Indexof

ConsumerConfidence1990:21917231051990:329571901990:4638837611991:1312730651991:2274787733ConsumerConfidenceandthe193-4InvestmentEqualsSaving:AnAlternativeWayofThinkingaboutGoods-MarketEquilibriumSavingisthesumofprivatepluspublicsaving.Privatesaving(S),issavingbyconsumers.Publicsavingequalstaxesminusgovernmentspending.IfT>G,thegovernmentisrunningabudgetsurplus—publicsavingispositive.IfT<G,thegovernmentisrunningabudgetdeficit—publicsavingisnegative.343-4InvestmentEqualsSaving:Theequationabovestatesthatequilibriuminthegoodsmarketrequiresthatinvestmentequalssaving—thesumofprivatepluspublicsaving.ThisequilibriumconditionforthegoodsmarketiscalledtheISrelation.Whatfirmswanttoinvestmustbeequaltowhatpeopleandthegovernmentwanttosave.3-4InvestmentEqualsSaving:AnAlternativeWayofThinkingaboutGoods-MarketEquilibrium35TheequationabovestatesthatConsumptionandsavingdecisionsareoneandthesame.Theterm(1c1)iscalledthepropensitytosave.Inequilibrium:Rearrangingterms,wegetthesameresultasbefore:InvestmentEqualsSaving:AnAlternative

WayofThinkingaboutGoods-MarketEquilibrium36Consumptionandsavingdecisio求解均衡所得37求解均衡所得37TheParadoxofSavingTheparadoxofsaving(ortheparadoxofthrift)isthataspeopleattempttosavemore,theresultisbothadeclineinoutputandunchangedsaving.38TheParadoxofSavingTheparad均衡所得變動—政府部門主旨：政府支出及租稅(均視為外生決定或自發性)等財政政策的對(均衡)所得的作用均衡：均衡所得基本上為自發支出×乘數

Y＝1/(1－c1)×(Co＋Io＋Go－c1To)乘數：政府支出乘數＝ΔY/ΔG＝1/(1－c1)租稅乘數＝ΔY/ΔT＝－c1/(1－c1)

平衡預算乘數＝1，在政府支出與租稅同額同向調整以保持預算平衡下，所得等額變動。39均衡所得變動—政府部門主旨：39穩定或權宜性的財政政策穩定財政政策(stabilizationfiscalpolicy)或權宜性的財政政策(discretionaryfiscalpolicy)景氣過熱，則採緊縮性財政政策，降低政府支出或提高租稅景氣衰退，則採擴張性財政政策，增加政府支出或降低租稅緊縮缺口(deflationaryorrecessionarygap)：均衡所得低於充分就業之所得時，自發支出低於充分就業之支出水準，稱之。此時，採增加政府支出或降低租稅(擴張性財政政策)可解決。膨脹缺口(inflationarygap)：均衡所得高於充分就業之所得時，自發支出超過充分就業之支出水準，稱之。此時，採降低政府支出或提高租稅(緊縮性財政政策)可解決(免除物價膨脹壓力)。40穩定或權宜性的財政政策穩定財政政策(stabilizatio自動安定機能(built-instabilizer)指數財政制度中，具有可緩和景氣波動或波幅的自我調節功能。誘發性租稅：如(累進)所得稅，當景氣轉壞，可使消費不致於下降太多，轉好時可免過熱。也可降低外生變數變動對景氣影響程度，設T＝To＋tY時，自發支出乘數由1/(1－c1)縮小為1/(1－c1＋c1t)失業保險制：不景氣時，失業家庭可獲救濟金，使失業家庭消費不致於快速下降。41自動安定機能(built-instabilizer)指數財3-5IstheGovernmentOmnipotent?

AWarningChanginggovernmentspendingortaxesisnotalwayseasy.

Theresponsesofconsumption,investment,imports,etc,arehardtoassesswithmuchcertainty.

Anticipationsarelikelytomatter.

Achievingagivenlevelofoutputcancomewithunpleasantsideeffects.

Budgetdeficitsandpublicdebtmayhaveadverseimplicationsinthelongrun.423-5IstheGovernmentOmnipot均衡所得決定與變動—國外部門主旨：考慮進出口貿易對(均衡)所得的作用出口擴張：國外景氣好轉、國外物價上升、國外進口障礙降低、本國物價下降、本國貨幣貶值、出口鼓勵措施----。進口增加：本國所得提高、物價上漲、本國貨幣升值、進口品價格下跌、降低關稅及進口管制---。函數：出口是外生EX＝EXo，進口是所得函數

IM＝IMo＋mY，m是邊際進口傾向。均衡所得：Y＝1/(1－c1＋m)×(Co＋Io＋Go＋EXo－IMo－c1To)，此時I＋G＋EX＝S＋T＋IM乘數：(出口)自發支出乘數＝1/(1－c1＋m)，自發進口乘數＝－1/(1－c1＋m)43均衡所得決定與變動—國外部門主旨：考慮進出口貿易對(z總支出函數與均衡所得

單位：億元YCIoGoEXoIMNXAE30024060906030304204003106090604020480500380609060501054060045060906060060070052060906070-1066080059060906080-2072044z總支出函數與均衡所得KeyTermsConsumption(C)Investment(I)FixedinvestmentNonresidentialinvestmentResidentialinvestmentGovernmentspending(G)GovernmenttransfersImports(IM)Exports(X)Netexports(X-IM)TradebalanceTradesurplusTradedeficitInventoryinvestmentIdentityDisposableincome(YD)ConsumptionfunctionBehavioralequationLinearrelationParameterPropensitytoconsume(c1)EndogenousvariablesExogenousvariablesFiscalpolicyEquilibriumEquilibriuminthegoodsmarketEquilibriumconditionAutonomousspendingBalancedbudgetMultiplierGeometricseriesEconometricsDynamicsForecasterrorConsumerconfidenceindexPrivatesaving(S)Publicsaving(T-G)BudgetsurplusBudgetdeficitSavingISrelationPropensitytosaveParadoxofsaving45KeyTermsConsumption(C)Exogench03财货市场均衡凯因斯课件頭腦體操？為什麼會有失業？造成的原因是什麼？1930年代經濟大恐慌，為何有普遍失業的現象?失業產生究竟是因為企業生產萎縮(供給不足)所致，還是商品賣不出去(需求不足)所致?近一二年，全球及台灣普遍高失業率的現象，是供給面還是需求面所引起？台灣經濟不好，是那裡出了問題？中央要「拼經濟，救台灣」，如何拼法呢？過去台灣經濟不好時，政府總會提出振興投資方案、擴大內需政策---等，建立在什麼觀點上？你認為成效又如何？增加一元的投資支出或政府支出，可創造比一元還多的產出或所得，可能嗎？為何？決定家計消費支出的因素為何？決定企業投資的關鍵又如何？「節儉是美德」嗎？一經濟社會人們想增加儲蓄，是否整個經濟社會儲蓄水準就會增加？政府財政政策，如何能達到經濟穩定的目的？利用何種財政工具？國外經濟不景氣，台灣經濟跟著不好，如何說明這種現象？頭腦體操？為什麼會有失業？造成的原因是什麼？簡單凱因斯模型--理論基礎依據：凱因斯1936年「就業、利息與貨幣的一般理論」，1930年代經濟大恐慌提出。是需要面經濟學，主要說明失業為何產生及如何解決失業問題。當時勞動未充分就業，工資又無法向下調整，使企業缺乏增加勞動雇用的誘因。解決失業問題之法在提高總需求，貨暢其流，東西有銷路，生產增加，勞動需求自然增加。古典經濟學：是供給面經濟學，經由自由市場的價格機能，經濟常處於充分就業狀態，資本、技術、勞動供給量等生產能量決定總供給，總需求只影響物價水準而已。模式：依總合供需圖而言凱因斯學派—AS水平，產出與就業決定於總需求。古典學派—AS垂直，產出與就業決定於總供給，總需求只影響物價水準。中間區—AS正斜率，總需求與總供給共同決定產出、就業與物價。假定：物價不變，不計利率或金融(貨幣)面的作用(本章)主旨：民間消費、企業投資、政府支出、對外貿易如何影響一國所得48簡單凱因斯模型--理論基礎依據：凱因斯1936年「就業、利息3-1TheCompositionofGDPTable3-1TheCompositionofU.S.GDP,2006Billionsofdollars

PercentofGDPGDP(Y)13,246100.01Consumption(C)9,26970.02Investment(I)2,16316.3Nonresidential

1,39610.5Residential7675.83Governmentspending(G)2,52819.04Netexports7635.8

Exports(X)1,46611.0

Imports(IM)2,22916.85Inventoryinvestment490Source:SurveyofCurrentBusiness,April2007,Table1-1-5.493-1TheCompositionofGDPTab3-1TheCompositionofGDPConsumption(C)referstothegoodsandservicespurchasedbyconsumers.

Investment(I),sometimescalledfixedinvestment,isthepurchaseofcapitalgoods.Itisthesumofnonresidentialinvestmentandresidentialinvestment.

GovernmentSpending(G)referstothepurchasesofgoodsandservicesbythefederal,state,andlocalgovernments.Itdoesnotincludegovernmenttransfers,norinterestpaymentsonthegovernmentdebt.503-1TheCompositionofGDPCon3-1TheCompositionofGDPImports(IM)arethepurchasesofforeigngoodsandservicesbyconsumers,businessfirms,andtheU.S.government.

Exports(X)arethepurchasesofU.S.goodsandservicesbyforeigners.513-1TheCompositionofGDPImp3-1TheCompositionofGDPInventoryinvestmentisthedifferencebetweenproductionandsales.Netexports(XIM)isthedifferencebetweenexports

andimports,alsocalledthetradebalance.523-1TheCompositionofGDPInv3-2TheDemandforGoodsThetotaldemandforgoodsiswrittenas:Thesymbol“”meansthatthisequationisanidentity,ordefinition.TodetermineZ,somesimplificationsmustbemade:

Assumethatallfirmsproducethesamegood,whichcanthenbeusedbyconsumersforconsumption,byfirmsforinvestment,orbythegovernment.

533-2TheDemandforGoodsThet3-2TheDemandforGoodsAssumethatfirmsarewillingtosupplyanyamountofthegoodatagivenprice,P,anddemandinthatmarket.

Assumethattheeconomyisclosed,thatitdoesnottradewiththerestoftheworld,thenbothexportsandimports

arezero.Undertheassumptionthattheeconomyisclosed,

X=IM=0,then:543-2TheDemandforGoods93-2TheDemandforGoodsDisposableincome,(YD),istheincomethatremainsonceconsumershavepaidtaxesandreceivedtransfersfromthegovernment.ThefunctionC(YD)iscalledtheconsumptionfunction.Itisabehavioralequation,thatis,itcapturesthebehaviorofconsumers.Consumption(C)Amorespecificformoftheconsumptionfunctionisthislinearrelation:553-2TheDemandforGoodsDispo簡單凱因斯模型—民間消費與儲蓄影響消費支出的因素：可支配所得、利率、未來預期、資產或財富多寡、物價水準、貸款信用的條件與數量、所得分配狀況、家庭人口數與年齡結構。消費支出與可支配所得關係：凱恩斯提出消費基本心理法則(fundamentalpsychologicallaw)

所得增加消費支出增加；但消費額增量小於所得增量；且隨所得增加，平均消費額下降。消費函數：C＝co＋c1YD，Co是自發性消費、c1YD是誘發性消費，0＜c1＜1。消費傾向：邊際消費傾向(MPC)＝ΔC/ΔYD＝c

平均消費傾向(APC)＝C/YD＝(co/YD

)＋c1＞MPC儲蓄函數：S＝YD－C＝－co＋(1－c1)YD，

MPS＝ΔS/ΔYD，APS＝S/YD

消費傾向與儲蓄傾向關係：MPC＋MPS＝1，APC＋APS＝156簡單凱因斯模型—民間消費與儲蓄影響消費支出的因素：可支配所得可支配所得、消費、儲蓄

單位：萬元YCS△Y△C△SAPCAPSMPCMPC06-6-------1012-210641.2-20.60.4201821060.4302441060.440301010640.750361410640.720.280.60.460421810640.700.300.60.470482210640.690.310.60.457可支配所得、消費、儲蓄3-2TheDemandforGoodsThisfunctionhastwoparameters,c0andc1:

c1iscalledthe(marginal)propensitytoconsume,ortheeffectofanadditionaldollarofdisposableincomeonconsumption.

c0istheinterceptoftheconsumptionfunction. Disposableincomeisgivenby:Consumption(C)583-2TheDemandforGoodsThis3-2TheDemandforGoodsConsumption(C)Consumptionincreaseswithdisposableincomebutlessthanoneforone.ConsumptionandDisposableIncomeFigure3-1593-2TheDemandforGoodsConsu3-2TheDemandforGoodsVariablesthatdependonothervariableswithinthemodelarecalledendogenous.Variablesthatarenotexplainwithinthemodelarecalledexogenous.Investmenthereistakenasgiven,ortreatedasanexogenousvariable:

Investment(I)GovernmentSpending(G)Governmentspending,G,togetherwithtaxes,T,describesfiscalpolicy—thechoiceoftaxesandspendingbythegovernment.603-2TheDemandforGoodsVaria3-2TheDemandforGoods

WeshallassumethatGandTarealsoexogenousfortworeasons:

Governmentsdonotbehavewiththesameregularityasconsumersorfirms.

Macroeconomistsmustthinkabouttheimplicationsofalternativespendingandtaxdecisionsofthegovernment.613-2TheDemandforGoodsWes簡單凱因斯模型—投資支出定義：投資指新資本財的購買，資本財含機械設備、建築物(合稱固定資本)，及存貨變動。投資毛額＝投資淨額＋資本折舊，Kt＋1＝Kt＋It(投資毛額)－Dt＝Kt＋Int(投資淨額)影響投資需求因素：最適投資量決定於投資的邊際收益＝邊際成本成本方面—利率(投資的機會成本)下降、資本財價格下降，投資需求增加；反之，則減少。收益方面—產品未來銷售量或價格看好、技術改良或創新出現、資本設備利用率高、生產成本降低、稅捐減輕，投資需求增加；反之，則減少。

(政府公共投資有助於改善投資環境，而降低民間生產成本，提高民間投資意願；但擴大支出以發行大量公債支應，可能刺激利率上揚，不利民間投資。)投資函數：I＝I(i，Y)，i是利率，Y是所得62簡單凱因斯模型—投資支出定義：投資指新資本財的購買，資本財含3-3TheDeterminationofEquilibriumOutputAssumingthatexportsandimportsarebothzero,thedemandforgoodsisthesumofconsumption,investment,andgovernmentspending:Then:633-3TheDeterminationofEquiEquilibriuminthegoodsmarketrequiresthatproduction,Y,beequaltothedemandforgoods,Z:Then:Theequilibriumconditionisthat,production,Y,beequaltodemand.Demand,Z,inturndependsonincome,Y,whichitselfisequaltoproduction.3-3TheDeterminationofEquilibriumOutput64Equilibriuminthegoodsmarke3-3TheDeterminationofEquilibriumOutputMacroeconomistsalwaysusethesethreetools:AlgebratomakesurethatthelogiciscorrectGraphstobuildtheintuitionWordstoexplaintheresults653-3TheDeterminationofEqui3-3TheDeterminationofEquilibriumOutput

Rewritetheequilibriumequation:

UsingAlgebra

Movetotheleftsideandreorganizetherightside:

Dividebothsidesby663-3TheDeterminationofEquiTheequilibriumequationcanbemanipulatedtoderivesomeimportantterms:

Autonomousspendingandthemultiplier:Thetermisthatpartofthedemandforgoodsthatdoesnotdependonoutput,itiscalledautonomousspending.Ifthegovernmentranabalancedbudget,thenT=G.Becausethepropensitytoconsume(c1)isbetweenzeroandone,isanumbergreaterthanone.Forthisreason,thisnumberiscalledthemultiplier.3-3TheDeterminationofEquilibriumOutputUsingAlgebra67Theequilibriumequationcanb均衡所得決定—封閉經濟假定：不計國外部門，投資需求、政府支出外生決定，租稅為定額稅。均衡：Z=AE＝Y，預擬總支出(C+I+G消費支出、投資支出政府支出)與總產出或所得相等；Y＝1/(1－c1)×(co＋I0+G-c1T0)或原先打算進行的預擬(或事前)投資與預擬儲蓄相等，S＝I。(國民所得帳之C,S,I是事後或實際發生的數量，實現的儲蓄必恆等於實現的投資)如Z=AE＞Y或I＞S，表非意願存貨減少，企業增加生產，所得增加，直到Z=AE＝Y為止。如Z=AE＜Y或I＜S，表非意願存貨增加，企業減少生產，所得下降，直到Z=AE＝Y為止。68均衡所得決定—封閉經濟233-3TheDeterminationofEquilibriumOutputFirst,plotproductionasafunctionofincome.Second,plotdemandasafunctionofincome.InEquilibrium,productionequalsdemand.Equilibriumoutputisdeterminedbytheconditionthatproductionbeequaltodemand.EquilibriumintheGoodsMarketFigure3-2UsingaGraph693-3TheDeterminationofEquiUsingaGraphAnincreaseinautonomousspendinghasamorethanone-for-oneeffectonequilibriumoutput.TheEffectsofanIncreaseinAutonomousSpendingonOutputFigure3-33-3TheDeterminationofEquilibriumOutput70UsingaGraphAnincreaseinauUsingaGraphThefirst-roundincreaseindemand,shownbythedistanceABequals$1billion.Thisfirst-roundincreaseindemandleadstoanequalincreaseinproduction,or$1billion,whichisalsoshownbythedistanceinAB.Thisfirst-roundincreaseinproductionleadstoanequalincreaseinincome,shownbythedistanceinBC,alsoequalto$1billion.3-3TheDeterminationofEquilibriumOutput71UsingaGraphThefirst-roundiUsingaGraphThesecond-roundincreaseindemand,shownbythedistanceinCD,equals$1billiontimesthepropensitytoconsume.Thissecond-roundincreaseindemandleadstoanequalincreaseinproduction,alsoshownbythedistanceDC,andthusanequalincreaseinincome,shownbythedistanceDE.Thethird-roundincreaseindemandequals$c1billion,timesc1,themarginalpropensitytoconsume;itisequalto$c1

xc1

=$c12billion.3-3TheDeterminationofEquilibriumOutput72UsingaGraphThesecond-roundFollowingthislogic,thetotalincreaseinproductionafter,say,n+1

rounds,equals$1billionmultipliedbythesum:1+c1+c12+…+c1nSuchasumiscalledageometricseries.3-3TheDeterminationofEquilibriumOutputUsingaGraph73Followingthislogic,thetotaTosummarize:Anincreaseindemandleadstoanincreaseinprod