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1、A-Level经济学习笔记:总需求和总供给篇-收入的循环流动Thistopiciscalled,Aggregatedemandandsupply.Butbeforewelookattheseconcepts,itisimportantthatyouunderstandthe,bigpicture1.Thecircularflowofincomeisagoodplacetostart.Itshowsallofthemoneycomingintoaneconomy(injections)andallofthemoneythatgoesoutofaneconomy(leakagesorwithdra
2、wals).Itallowsyoutoseethe,general,reasonswhyaneconomymightgroworshrinkinsize.Onceyoucanseethe,bigpicture1wecanthenlookatthespecificsofaggregatedemandandaggregatesupply.这部分被称为“总需求和总供应,在我们了解概念之前,需要有“大局观”。收入的循环流动是一个很好的起点。它显示了进入经济体的所有资金(注入)和流出经济体的所有资金(泄漏或取款)。它使您可以了解经济规模可能增长或缩小的“一般”原因。一旦您看到“大图”,我们就可以查看总需
3、求和总供给的细节。The,2-sector,modelHOUSEHOLDSGOODS ANDSERVICES(OUTPUT)人EXPENDITUREON GOODS“AND SERVICES(EXPENDITURE)FIRMSLAND LABOUR CAPITAL让我们从最简单的模型开始。假定经济仅由以下两个部门组成:家庭households和企业firmsoRENTWAGESPROFIT八ANDINTEREST(INCOME)Inthisverysimplemodelofthewholeeconomy,itisassumedthatthehouseholdsownallthefactorso
4、fproduction.Theysellthesefactorstothefirms,earningrentontheirland,wagesfortheuseoftheirlabour,andprofitandinterestfortheuseoftheircapital.Thisisshownonthelefthandsideofthediagram.Thegreenlineshowsthefactorsofproductiongoingfromthehouseholdstothefirmsandtheredlineshowsthemoneypaymentsbythefirmsforthe
5、sefactorsgoingbacktothehouseholds.在整个经济的这个非常简单的模型中,假设家庭拥有所有的生产要素。他们将这些要素卖给企业,在他们的土地上赚取租金,为使用他们的劳动赚取工资,为使用他们的资本赚取利润和利息。这显示在图表的左侧。绿线表示生产要素从家庭流向企业,红线表示企业为这些要素流向家庭的货币支付。Thefirmsthenusethesefactorstoproducegoodsandservices.Andwhobuysthesegoodsandservices?Thehouseholds,ofcourse,usingtheincometheyearnedfro
6、mthesaleoftheirfactors.Thisisshownontherighthandsideofthediagram.Again,thegreenlinerepresentsmovementsofthephysicalandtheredlineshowsthemovementofthemoney.然后,这些公司利用这些因素来生产商品和服务。谁购买这些商品和服务?当然,这些家庭使用他们从出售他们的要素中获得的收入。这显示在图表的右侧。同样,绿线代表实物的走势,红线代表货币的走势。Althoughthismodelisverysimple,itdoesemphasiseoneveryi
7、mportantpoint.Whenmeasuringthesizeofaneconomy,orthelevelofeconomicactivity,therearethreewaysofdoingit.Inthediagramaboveyoucanseethatthreeofthefourmovinglineshavealsobeenlabelledinblack.The,rent,wages,profitandincome1branchrepresentstotalincomeoftheeconomy.The,goodsandservices1branchrepresentsthetota
8、loutputoftheeconomyandthe,expenditureongoodsandservices*branchrepresentsthetotalexpenditureoftheeconomy.虽然这个模型很简单,但它确实强调了一个非常重要的点。在衡量一个经济体的规模或经济活动的水平时,可以通过三种方式来衡量。在上图中,您可以看到四条移动线中的三条也被标记为黑色。“租金、工资、利润和收入分支代表经济的总收入。“商品和服务”部门代表经济的总产出,“商品和服务支出”部门代表经济的总支出。Sothesizeofaneconomycanbemeasuredusingeitherthein
9、come,outputorexpendituremethod.Noticethatthethreemethodsshouldgiveexactlythesameanswer.Itisfairlyobviousthattheamountofmoneyspentmustequalthevalueofthegoodsandservicesthatthismoneyisspenton.Althoughlessobvious,itshouldmakesensethattheamountofmoneyspentwillequaltheincomeofthespenders,assumingthatnone
10、ofthisincomeissaved.Thisbringsustoanotherkeypoint.Therearenoinjectionsintothiscircularflowandnoleakagesfromthecircularflow(likesaving)atthisstage.Hence,Income=Output=Expenditure.因此,一个经济体的规模可以使用收入、产出或支出方法来衡量。请注意,这三种方法应该给出完全相同的答案。很明显,花费的金额必须等于所花费的商品和服务的价值。虽然不那么明显,但假设这些收入都没有被储蓄,那么花费的金额将等于支出者的收入应该是有意义的。
11、这给我们带来了另一个关键点。在这个阶段,没有注入到这个循环流中,也没有从循环流中泄漏(如储蓄)。因此,收入二产出二支出。Includingleakagesandinjections在这个简单的模型中,到目前为止,我们假设系统是完全封闭的。不过,可以公平地假设,家庭不会花掉他们所有的收入,而且公司有时会投资于新资本。RENTWAGESPROFIT八ANDINTEREST(Y)HOUSEHOLDS1.ANDLABOURCAPITALGOODSANDSERVICES,SAVINGS(三)EXPENDITUREONGOODS“ANDSERVICES(C)FIRMSiiINVESTMENT(I)上图将第
12、一个循环流程图更进一步。两条蓝线表示储蓄从经济中流出和投资注入经济。储蓄漏水到哪里去,投资注入从哪里来?简而言之,储蓄存入银行部门或资本市场,而公司则从同一种来源借钱进行投资。Inthefirstdiagram,E(Expenditure)-O(Output)-Y(Income).Nowtherearetwotypesofexpenditure:consumption(byhouseholds)andinvestment(byfirms),SoE-C+I.Also,thehouseholds?incomeisnotallspentanymore.Someofitissaved,soY=C+S.
13、Weknowthatinequilibrium,Y=E,sobysubstitutingwehave:在第一个图中,E(支出)二0(产出)=Y(收入)。现在有两种支出:消费(家庭)和投资(企业),所以E=C+Io还有,家庭?收入不再全部花掉。其中一些被保存,所以Y=C+S。我们知道在平衡状态下,Y=E,所以通过代入我们有:Y=EC+S=C+IS=I(bycancellingouttheCs)Sowecanseethatinthis2-sectormodel,actualinvestment(theinjection)mustequalactualsaving(theleakage).Itmak
14、essensethattheinjectionsshouldequalwithdrawalsinequilibrium.Thinkofthecircularflowdiagramaswaterflowingthroughpipes,andthe,households,andfirmssquaresaswatertanks.Ifinjectionsweregreaterthanwithdrawals,theamountofwaterinthesystemwouldbecomeinfinite,whichdoesnftmakesense.Ifwithdrawalsweregreaterthanin
15、jections,afteratimetherewouldbenowaterinthesystem,whichalsodoesn,tmakesense.所以我们可以看到,在这个2部门模型中,实际投资(注入)必须等于实际储蓄(泄漏)。在平衡状态下,注入应该等于退出是有道理的。将圆形流程图想象为流经管道的水,将“家庭”和“公司”方格想象成水箱。如果注入量大于取量量,系统中的水量将变得无限,这是没有意义的。如果提取量大于注射量,那么一段时间后系统中将没有水,这也没有意义。Althoughtheamountthathouseholdsplantosavemaynotbethesameastheamountthatfirmsplantoinvest,theactualamountsarealwaysequal.Iftheplansarenotthesame,thefirms,stocklevels(whichcountasinvestment)willadjustuntilactualinvestment(plannedinvestmentplusunplannedchangesinthestocklevel)equalsactualsaving.Ofcourse,theeconomyison