A-Level經(jīng)濟(jì)學(xué)可以稱得上是A-Level文科的“萬(wàn)金油學(xué)科”了，幾乎所有大學(xué)的商科類專業(yè)都接受A-Level經(jīng)濟(jì)學(xué)的成績(jī)，同時(shí)A-Level經(jīng)濟(jì)學(xué)還是經(jīng)濟(jì)類、管理類、商科類、營(yíng)銷類、金融類專業(yè)的優(yōu)勢(shì)學(xué)科，能夠有效的提高學(xué)生的錄取率。

今天A加未來(lái)就給各位同學(xué)們分享一篇A-Level經(jīng)濟(jì)學(xué)總需求和總供給篇-收入的循環(huán)流動(dòng) The Circular Flow of Income筆記：

This topic is called?'Aggregate demand and supply.?But before we look at these concepts, it is important that you understand the 'big picture'.

The?circular flow of income?is a good place to start.

It shows all of the money coming into an economy (injections) and all of the money that goes out of an economy (leakages?or?withdrawals).

It allows you to see the 'general' reasons why an economy might grow or shrink in size.

Once you can see the 'big picture' we can then look at the specifics of?aggregate demand?and?aggregate supply.

這部分被稱為“總需求和總供應(yīng)”，在我們了解概念之前，需要有“大局觀”。收入的循環(huán)流動(dòng)是一個(gè)很好的起點(diǎn)。它顯示了進(jìn)入經(jīng)濟(jì)體的所有資金（注入）和流出經(jīng)濟(jì)體的所有資金（泄漏或取款）。它使您可以了解經(jīng)濟(jì)規(guī)?？赡茉鲩L(zhǎng)或縮小的“一般”原因。一旦您看到“大圖”，我們就可以查看總需求和總供給的細(xì)節(jié)。

The '2-sector' model

讓我們從最簡(jiǎn)單的模型開始。假定經(jīng)濟(jì)僅由以下兩個(gè)部門組成：家庭households和企業(yè)firms。

In this very simple model of the whole economy, it is assumed that the households own all the?factors of production.

They sell these factors to the firms, earning rent on their land, wages for the use of their labour, and profit and interest for the use of their capital.

This is shown on the left hand side of the diagram.

The green line shows the factors of production going from the households to the firms and the red line shows the money payments by the firms for these factors going back to the households.

在整個(gè)經(jīng)濟(jì)的這個(gè)非常簡(jiǎn)單的模型中，假設(shè)家庭擁有所有的生產(chǎn)要素。他們將這些要素賣給企業(yè)，在他們的土地上賺取租金，為使用他們的勞動(dòng)賺取工資，為使用他們的資本賺取利潤(rùn)和利息。

這顯示在圖表的左側(cè)。綠線表示生產(chǎn)要素從家庭流向企業(yè)，紅線表示企業(yè)為這些要素流向家庭的貨幣支付。

The firms then use these factors to produce goods and services. And who buys these goods and services?

The households, of course, using the income they earned from the sale of their factors.

This is shown on the right hand side of the diagram.

Again, the green line represents movements of the physical and the red line shows the movement of the money.

然后，這些公司利用這些因素來(lái)生產(chǎn)商品和服務(wù)。誰(shuí)購(gòu)買這些商品和服務(wù)？當(dāng)然，這些家庭使用他們從出售他們的要素中獲得的收入。這顯示在圖表的右側(cè)。同樣，綠線代表實(shí)物的走勢(shì)，紅線代表貨幣的走勢(shì)。

Although this model is very simple, it does emphasise one very important point.

When measuring the size of an economy, or the level of economic activity, there are three ways of doing it.

In the diagram above you can see that three of the four moving lines have also been labelled in black. The 'rent, wages, profit and income' branch represents?total income?of the economy.

The 'goods and services' branch represents the?total output?of the economy and the 'expenditure on goods and services' branch represents the?total expenditure?of the economy.

雖然這個(gè)模型很簡(jiǎn)單，但它確實(shí)強(qiáng)調(diào)了一個(gè)非常重要的點(diǎn)。在衡量一個(gè)經(jīng)濟(jì)體的規(guī)模或經(jīng)濟(jì)活動(dòng)的水平時(shí)，可以通過(guò)三種方式來(lái)衡量。在上圖中，您可以看到四條移動(dòng)線中的三條也被標(biāo)記為黑色?！白饨稹⒐べY、利潤(rùn)和收入”分支代表經(jīng)濟(jì)的總收入?！吧唐泛头?wù)”部門代表經(jīng)濟(jì)的總產(chǎn)出，“商品和服務(wù)支出”部門代表經(jīng)濟(jì)的總支出。

So the size of an economy can be measured using either the?income,?output or expenditure method.

Notice that the three methods should give exactly the same answer. It is fairly obvious that the amount of money spent must equal the value of the goods and services that this money is spent on.

Although less obvious, it should make sense that the amount of money spent will equal the income of the spenders, assuming that none of this income is saved.

This brings us to another key point. There are no?injections?into this circularflow and no?leakages?from the circular flow (like saving) at this stage. Hence,?Income = Output = Expenditure.

因此，一個(gè)經(jīng)濟(jì)體的規(guī)?？梢允褂?strong>收入、產(chǎn)出或支出方法來(lái)衡量。請(qǐng)注意，這三種方法應(yīng)該給出完全相同的答案。很明顯，花費(fèi)的金額必須等于所花費(fèi)的商品和服務(wù)的價(jià)值。雖然不那么明顯，但假設(shè)這些收入都沒(méi)有被儲(chǔ)蓄，那么花費(fèi)的金額將等于支出者的收入應(yīng)該是有意義的。這給我們帶來(lái)了另一個(gè)關(guān)鍵點(diǎn)。在這個(gè)階段，沒(méi)有注入到這個(gè)循環(huán)流中，也沒(méi)有從循環(huán)流中泄漏（如儲(chǔ)蓄）。因此，收入 = 產(chǎn)出 = 支出。

Including leakages and injections

在這個(gè)簡(jiǎn)單的模型中，到目前為止，我們假設(shè)系統(tǒng)是完全封閉的。不過(guò)，可以公平地假設(shè)，家庭不會(huì)花掉他們所有的收入，而且公司有時(shí)會(huì)投資于新資本。

上圖將第一個(gè)循環(huán)流程圖更進(jìn)一步。兩條藍(lán)線表示儲(chǔ)蓄從經(jīng)濟(jì)中流出和投資注入經(jīng)濟(jì)。儲(chǔ)蓄漏水到哪里去，投資注入從哪里來(lái)？簡(jiǎn)而言之，儲(chǔ)蓄存入銀行部門或資本市場(chǎng)，而公司則從同一種來(lái)源借錢進(jìn)行投資。

In the first diagram, E (Expenditure) = O (Output) = Y (Income).

Now there are two types of expenditure: consumption (by households) and investment (by firms), So E = C + I.

Also, the households?

income is not all spent anymore. Some of it is saved, so Y = C + S.

We know that in equilibrium, Y = E, so by substituting we have:

在第一個(gè)圖中，E（支出）= O（產(chǎn)出）= Y（收入）?，F(xiàn)在有兩種支出：消費(fèi)（家庭）和投資（企業(yè)），所以E = C + I。還有，家庭？收入不再全部花掉。其中一些被保存，所以 Y = C + S。我們知道在平衡狀態(tài)下，Y = E，所以通過(guò)代入我們有：

So we can see that in this 2-sector model, actual investment (the injection) must equal actual saving (the leakage).

It makes sense that the injections should equal withdrawals in equilibrium.

Think of the circular flow diagram as water flowing through pipes, and the 'households' and 'firms' squares as water tanks.

If injections were greater than withdrawals, the amount of water in the system would become infinite, which doesn't make sense.

If withdrawals were greater than injections, after a time there would be no water in the system, which also doesn't make sense.

所以我們可以看到，在這個(gè) 2 部門模型中，實(shí)際投資（注入）必須等于實(shí)際儲(chǔ)蓄（泄漏）。在平衡狀態(tài)下，注入應(yīng)該等于退出是有道理的。將圓形流程圖想象為流經(jīng)管道的水，將“家庭”和“公司”方格想象成水箱。如果注入量大于取量量，系統(tǒng)中的水量將變得無(wú)限，這是沒(méi)有意義的。如果提取量大于注射量，那么一段時(shí)間后系統(tǒng)中將沒(méi)有水，這也沒(méi)有意義。

Although the amount that households?plan?to save may not be the same as the amount that firms?plan?to invest, the actual amounts are always equal.

If the plans are not the same, the firms' stock levels (which count as investment) will adjust until actual investment (planned investment plus unplanned changes in the stock level) equals actual saving.

Of course, the economy is only in an equilibrium position if the plans are the same.

Otherwise, firms will find their stocks build up (or disappear) and change their output levels accordingly to allow for the different saving plans (and, therefore, consumption plans) of the households.

盡管家庭計(jì)劃儲(chǔ)蓄的金額可能與公司計(jì)劃投資的金額不同，但實(shí)際金額總是相等的。

如果計(jì)劃不同，公司的存量水平（計(jì)為投資）將調(diào)整，直到實(shí)際投資（計(jì)劃投資加上存量水平的計(jì)劃外變化）等于實(shí)際儲(chǔ)蓄。當(dāng)然，只有在計(jì)劃相同的情況下，經(jīng)濟(jì)才會(huì)處于均衡狀態(tài)。否則，公司會(huì)發(fā)現(xiàn)他們的庫(kù)存增加（或消失）并相應(yīng)地改變他們的產(chǎn)出水平，以適應(yīng)家庭的不同儲(chǔ)蓄計(jì)劃（因此，消費(fèi)計(jì)劃）。

It does make sense that?savings equals investment.?In most economies in the world, the amount that is invested over the long term is closely related tothe amount that the economy saves.

The UK traditionally has quite a low?savings ratio, especially when the economy is doing well, and this has been translated into a poor record on investment over the years.

In Japan, the savings ration is very large.

Investment is also high in Japan, as is their investment in projects abroad.

儲(chǔ)蓄等于投資是有道理的。在世界上大多數(shù)經(jīng)濟(jì)體中，長(zhǎng)期投資的金額與經(jīng)濟(jì)體的儲(chǔ)蓄金額密切相關(guān)。傳統(tǒng)上，英國(guó)的儲(chǔ)蓄率相當(dāng)?shù)?/strong>，尤其是在經(jīng)濟(jì)表現(xiàn)良好的情況下，這已轉(zhuǎn)化為多年來(lái)的投資記錄不佳。在日本，儲(chǔ)蓄率非常大。日本的投資也很高，他們對(duì)海外項(xiàng)目的投資也是如此。

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