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今天带给大家Alevel经济笔记是：

第4章：Exchange Rates—The Exchange Rate and the Balance of Payments

The theoretical link

理论链接

For those of you who have not read the previous Learn-It, here is a quick recap. Theoretically, a current account deficit should cause the value of the pound to fall.

In this case, the value of imports into the UK is higher than the value of exports sold to foreigners.

Hence, the demand for foreign currencies to buy these imports is higher than the demand for the pound to by our exports.

Simple supply and demand analysis, therefore, suggests that the value of the pound should fall. For a current account surplus , simply reverse the above explanation.

对于那些还没有读过之前的 Learn-It 的人，这里有一个快速回顾。从理论上讲， 经常账户赤字 应该会导致英镑贬值。在这种情况下，进入英国的进口价值高于出售给外国人的出口价值。因此，购买这些进口商品的外汇需求高于我们的出口商品对英镑的需求。因此，简单的供需分析表明英镑应该下跌。对于 经常账户盈余 ，只需颠倒上述解释即可。

In the case of a deficit, the subsequent lower value of the pound will make exports relatively cheaper and imports relatively more expensive.

The value of exports sold should rise and the value of imports bought should fall. The deficit should be eliminated automatically (again, reverse the explanation for a surplus).

在出现逆差的情况下，英镑随后的贬值将使出口相对便宜，进口相对昂贵。出口的出口价值应该上升，进口的价值应该下降。赤字应该自动消除（再次，颠倒对盈余的解释）。

This story worked well until the controls on the world capital markets were lifted.

Once capital could go wherever it wanted, currency transactions for investment and speculative purposes took over.

A country's trade position is no longer relevant. If an economy is doing well, which usually means that consumer spending is high (spending on imports in particular), a current account deficit is expected.

Perversely, instead of the currency falling for the reasons outlined above, the currency is as likely to rise, because investors and speculators like to place their money on 'winners' (for example, economies that are doing well).

In fact, a currency may even rise following a cut in interest rates (which would normally cause the currency to fall following the outflow of money trying to find better rates elsewhere) because the markets may take it as a sign that the economy will improve in the future!

See the previous Learn-It for more discussion on the determination of the exchange rate.

在解除对世界资本市场的控制之前，这个故事一直很奏效。一旦资本可以去任何它想去的地方，用于投资和投机目的的货币交易就会接管。一个国家的贸易地位不再重要。如果一个经济体表现良好，这通常意味着消费者支出很高（尤其是进口支出），那么经常账户就会出现赤字。反常的是，由于投资者和投机者喜欢将资金投向“赢家”（例如，表现良好的经济体），而不是由于上述原因货币贬值，货币可能会上涨。实际上，一种货币甚至可能在降息后上涨（这通常会导致货币在资金外流试图在其他地方找到更好的利率后下跌），因为市场可能会将其视为未来经济将改善的迹象！有关确定汇率的更多讨论，请参阅前面的 Learn-It。

In the rest of this Learn-It, we shall be looking at the theoretical relationship between a change in the exchange rate and current account disequilibria.

在本次学习的其余部分中，我们将研究汇率变化与经常账户失衡之间的理论关系。

The Marshall Lerner condition

马歇尔勒纳条件

Assume that the UK has a current account deficit (which is not hard to do!). If the pound were to devalue (a large drop in its value) then one would expect the deficit to reduce.

Why ? Because exports will become relatively cheaper, and so their demand should rise in foreign markets, and imports will become relatively more expensive, so their demand should fall in the UK.

假设英国有经常账户赤字（这不难做到！）。如果英镑 贬值 （大幅贬值），那么人们会预期赤字会减少。 为什么 ？因为出口会变得相对便宜，所以他们在国外市场的需求应该会上升，而进口会变得相对更贵，所以他们在英国的需求应该会下降。

But will this always be the case?

The success of a devaluation of the pound in terms of reducing a current account deficit will depend on foreigners' elasticity of demand for British exports and UK consumer's elasticity of demand for foreign imports.

但这会一直如此吗？ 英镑贬值 能否成功减少经常账户赤字将取决于外国人对英国出口 的需求 弹性和英国消费者对外国进口的需求弹性。

The Marshall Lerner condition states that for a devaluation to be successful in terms of a reduced current account deficit, the sum of the two elasticities, must be greater than one.

Marshall Lerner 条件指出，要使经常账户赤字减少，贬值成功，两个弹性的总和必须大于 1。

To illustrate that this should be true, let's look at exports and imports separately.

为了说明这应该是正确的，让我们分别看看出口和进口。

Export elasticity

出口弹性

If you think about it, UK exporters can't go wrong if the pound falls in value.

How ever small the depreciation in the pound is, and however low the elasticity for their exports is, the revenue they will receive will have to rise.

如果您考虑一下，如果英镑贬值，英国出口商不会出错。 英镑贬值 多小，出口弹性多低，他们将获得的收入将不得不增加。

For example , let's take a car company that is exporting cars to the USA whose price is £10,000 in the UK.

Let us also assume that the exchange rate between these two countries is £1 = $2. These cars will have a price of $20,000 in the USA.

Now assume that the pound devalues by 10% so that the new exchange rate is £1 = $1.80. The price in the USA is now $18,000.

Unless the elasticity of demand for these cars in the USA is zero (highly unlikely) then the demand for these cars in the USA will increase.

Although American consumers now only have to pay $18,000, the British car company still receives £10,000 for each sale.

However large or small the fall in the value of the pound is, the sterling price of the car stays the same.

Even if this company only sells one extra car, they will still receive an extra £10,000.

例如 ，假设一家汽车公司向美国出口汽车，其在英国的价格为 10,000 英镑。我们还假设这两个国家之间的汇率为 1 英镑 = 2 美元。这些汽车在美国的售价为 20,000 美元。现在假设英镑贬值 10%，因此新汇率为 1 英镑 = 1.80 美元。现在在美国的价格是 18,000 美元。除非美国对这些汽车的需求弹性为零（极不可能），否则美国对这些汽车的需求将会增加。尽管美国消费者现在只需支付 18,000 美元，这家英国汽车公司仍然可以从每笔销售中获得 10,000 英镑。无论英镑贬值的幅度有多大，汽车的英镑价格都保持不变。即使这家公司只多售出一辆汽车，他们仍将获得额外的 10,000 英镑。

In summary, for export revenue to rise following a devaluation of the pound, the elasticity of demand for these exports simply has to be greater than zero (which is perfectly inelastic demand ).

Obviously, the higher the elasticity the bigger the increase in export revenue, but anything over zero will help reduce the current account deficit.

总之，要在英镑贬值后增加出口收入，这些出口的需求弹性必须大于零（这是 完全无弹性的需求 ）。显然，弹性越高，出口收入的增长就越大，但任何超过零的值都将有助于减少经常账户赤字。

Import elasticity

进口弹性

In the case of imports the situation is a little less favourable. A devaluation of the pound will cause the price of imports into the UK to rise.

The demand for these imports will fall, but the revenue that the foreign producers receive will not necessarily fall.

在进口的情况下，情况稍微不那么有利。英镑贬值将导致英国进口商品价格上涨。对这些进口产品的需求会下降，但外国生产商获得的收入不一定会下降。

For example, assume that an American car company exports their cars into the UK. The price for these cars in the USA is $30,000.

Again, assume that the initial exchange rate is £1 = $2.

This means that the price of these cars in the UK will be £15,000.

Now assume that the pound devalues by 25% giving an exchange rate of £1 = $1.50.

Swapping this exchange rate around to give the price of dollars in terms of pounds, we have $1 = £0.67.

So now the American cars are priced at £20,000 in the UK.

The change in the revenue received by the American car company will depend on the elasticity of demand for their cars in the UK.

例如，假设一家美国汽车公司将他们的汽车出口到英国。这些汽车在美国的价格是 30,000 美元。同样，假设初始汇率为 1 英镑 = 2 美元。这意味着这些汽车在英国的售价将达到 15,000 英镑。现在假设英镑贬值 25%，汇率为 1 英镑 = 1.50 美元。交换这个汇率以给出以英镑计的美元价格，我们有 1 美元 = 0.67 英镑。所以现在美国汽车在英国的售价为 20,000 英镑。这家美国汽车公司收入的变化将取决于英国对其汽车的需求弹性。

Assume that the elasticity is 1.5, which is relatively elastic .

As you will know from the topic called ' Elasticities ', if demand is relatively elastic and the price rises, the decrease in demand will be relatively larger.

This means that the loss in revenue from the decrease in demand is higher than the gain in revenue on each unit due to the higher price.

The diagram below helps to explain:

假设弹性为1.5，比较有 弹性 。正如您从“ 弹性 ”主题中所知道的，如果需求相对具有弹性并且价格上涨，则需求的下降幅度会相对较大。这意味着由于价格上涨，需求减少造成的收入损失高于每个单位的收入收益。下图有助于解释：

Note that the elastic demand curve is relatively flat, so that when the price rises, the fall in demand is relatively larger, and the 'gain' box is much smaller than the 'loss' box.

The more elastic the demand for UK imports is, the more successful a devaluation will be in terms of reducing import revenues (which go out of the country) and the bigger the reduction in the current account deficit.

注意，弹性需求曲线比较平坦，所以当价格上涨时，需求下降的幅度相对较大，“收益”框远小于“损失”框。对英国进口的需求越 富有弹性 ，贬值在减少进口收入（出口到国外）和经常账户赤字减少方面就越成功。

Now assume that the elasticity is 0.5, which is relatively inelastic .

Again, you should know that, in this case, when the price rises, the decrease in demand in relatively smaller.

This means that the loss in revenue from the decrease in demand is lower than the gain in revenue on each unit due to the higher price:

现在假设弹性为 0.5，相对 无弹性 。再次，你应该知道，在这种情况下，当价格上涨时，需求下降的幅度相对较小。这意味着由于价格较高，需求减少导致的收入损失低于每个单位的收入收益：

This demand curve is relatively inelastic, and so is fairly steep.

You can see that the price rise is proportionately much larger than the fall in demand, so the 'gain' box is much larger than the 'loss' box.

If the demand for UK imports is relatively inelastic then devaluation will result in increasing import revenues (which go out of the country), which contribute to a larger current account deficit.

这条需求曲线相对缺乏弹性，因此相当陡峭。您可以看到价格上涨的比例远大于需求下降，因此“收益”框比“损失”框大得多。如果对英国进口的需求相对 缺乏弹性 ，那么贬值将导致进口收入增加（出口到国外），从而导致经常账户赤字扩大。

Putting exports and imports together

将出口和进口放在一起

So, the condition for exports and imports separately can be summarised as follows:

因此，出口和进口分开的条件可以总结如下：

Eex > 0 for a devaluation to increase export revenues

E ex > 0 表示贬值以增加出口收入

Eim > 1 for a devaluation to reduce foreigners import revenue

E im > 1 贬值以减少外国人进口收入

By adding the zero and the one, we get the following overall condition:

通过添加零和一，我们得到以下整体条件：

Eex + Eim > 1 For a devaluation to be successful in terms of reducing a current account deficit.

E ex + E im > 1 贬值在减少经常账户赤字方面是成功的。

Note that, overall, as long as the two elasticities add up to more than one the devaluation will reduce the deficit, even if the two individual conditions above are not satisfied.

For example, if Eex = 0.6 and Eim = 0.6, import revenue will rise following a devaluation, but this will be more than compensated for by a larger rise in export revenue.

The elasticities add up to 1.2, which is more than one, so overall the situation improves.

Obviously, the higher both elasticities are, the more successful devaluation will be in terms of reducing the current account deficit.

请注意，总体而言，只要两个弹性加起来超过 1，即使不满足上述两个单独条件，贬值也会减少赤字。例如，如果 E ex = 0.6 和 E im = 0.6，则贬值后进口收入将增加，但这将被出口收入的更大增长所弥补。弹性加起来为 1.2，大于 1，因此总体情况有所改善。显然，这两种弹性越高，贬值在减少经常账户赤字方面就越成功。

The J-curveJ曲线

As the title suggests, this is a curve that is shaped like a 'J'. Look at the diagram below:

正如标题所示，这是一条形状像“J”的曲线。看下图：

Let us assume that the economy is at point A, experiencing a current account deficit.

The government decides to devalue the pound to help eliminate this deficit.

The J-curve shows that, in the short term, the deficit may get bigger before, eventually, it starts to reduce.

In other words, the Marshall Lerner condition is not satisfied in the short run, even though it will be in the medium to long term.

让我们假设经济处于 A 点，出现经常账户赤字。政府决定让英镑贬值以帮助消除这一赤字。J曲线表明，在短期内，赤字可能会变大，最终会开始减少。换句话说，马歇尔勒纳条件在短期内是不满足的，尽管它会在中长期内满足。

Why might this be the case?

The main reason is time lags. It takes time for producers and consumers to adjust their purchases to the changed prices brought about by the devalued exchange rate.

Certainly, firms will have orders planned in advance, and will not react to the price changes for a number of months.

为什么会这样？ 主要原因是时间滞后。生产者和消费者需要时间来调整购买以适应汇率贬值带来的价格变化。当然，公司会提前计划好订单，并且在几个月内不会对价格变化做出反应。

Exports revenues may not rise immediately, but they will not fall either, but foreign import revenues may well rise, as increased import prices are combined with static, or at least very inelastic, demand.

The current account deficit will probably get worse. After a period of time, foreigners will react to the lower export prices and UK firms and consumers will react to the higher import prices.

The Marshall Lerner condition should be satisfied as demand for both exports and imports become more elastic and the deficit should start to fall.

出口收入可能不会立即上升，但也不会下降，但外国进口收入很可能会上升，因为进口价格上涨与静态或至少非常缺乏弹性的需求相结合。经常账户赤字可能会变得更糟。一段时间后，外国人将对较低的出口价格做出反应，而英国公司和消费者将对较高的进口价格做出反应。随着出口和进口的需求变得更具弹性并且赤字应该开始下降，应该满足马歇尔勒纳条件。

Remember that higher import prices will feed through to higher inflation eventually.

This will reduce the competitiveness of British industry causing long-term problems for the current account. This is why many politicians see devaluation as failure.

Once the economy is past the trough of the J-curve and the deficit is falling, the devaluation may seem like a good idea.

But the subsequent rise in inflation (the government's number one macroeconomic objective nowadays) and its implications for competitiveness mean that devaluation is never a good long-term solution.

British exporters complain of the high pound, but devaluation will not necessarily do them any favours.

请记住，更高的进口价格最终会导致更高的通货膨胀。这将降低英国工业的竞争力，给经常账户带来长期问题。这就是为什么许多政客将贬值视为失败的原因。一旦经济越过了 J 曲线的低谷并且赤字正在下降，贬值似乎是个好主意。但随后的通胀上升（政府目前的首要宏观经济目标）及其对竞争力的影响意味着贬值绝不是一个好的长期解决方案。英国出口商抱怨英镑高企，但贬值不一定对他们有任何好处。

It should be noted that in today's world of free flowing capital, it is very hard (some would say impossible) for a government to actually implement a policy of devaluation.

The markets decide the country's exchange rate.

When the UK was part of the Bretton Woods fixed exchange rate system , occasional 'realignments' would occur (i.e. devaluations).

Now that the pound floats on the foreign exchange markets, the currency might appreciate (rise gently in value) or depreciate (fall gently in value) but big, one off drops in the value of the currency do not really happen.

The last big devaluation was when the pound fell out of the ERM and the pound fell by around 15% in one day.

应当指出，在当今资本自由流动的世界中，政府要真正实施贬值政策是非常困难的（有人会说不可能）。市场决定国家的汇率。当英国成为 布雷顿森林固定汇率体系 的一部分时，偶尔会发生“调整”（即贬值）。既然英镑在外汇市场上浮动，货币可能会 升值 （价值温和上升）或 贬值 （价值温和下降），但货币价值的大幅下降并没有真正发生。上一次大幅贬值是英镑脱离 ERM，一天之内英镑下跌了 15% 左右。

The 'upside down' J-curve“颠倒”的 J 曲线

The analysis above can work for countries with persistent current account surpluses that they want to eliminate. Look at the diagram below:

上述分析适用于那些想要消除经常账户盈余的国家。 看下图：

Assume that the economy is at point B, experiencing a current account surplus.

Rather than devaluation, the government will want to revalue their currency to make exports relatively more expensive (reducing their demand) and imports relatively cheaper (increasing their demand). Again, there will be time lags.

Consumers and producers will not react to these changes immediately.

The demand for both exports and imports will be relatively inelastic in the short run.

Export revenues will not change (a fixed UK price, remember) but the revenue paid for foreign imports will fall.

This will make the current account surplus get even bigger in the short run .

假设经济处于 B 点，出现经常账户盈余。与其贬值，政府将希望 重新评估 其货币，以使出口相对更昂贵（减少需求）和进口相对便宜（增加需求）。同样，会有时间滞后。消费者和生产者不会立即对这些变化做出反应。出口和进口的需求在短期内都将相对缺乏弹性。出口收入不会改变（记住英国的固定价格），但为外国进口支付的收入会下降。这将使经常项目顺差在 短期内 变得更大。

In the medium term, firms and consumers will adjust their purchases in line with the changed prices.

The demand for both exports and imports will become more elastic and the surplus will eventually start to fall.

The result is an upside down J-curve!

从中期来看，企业和消费者将根据价格变化调整购买。出口和进口的需求都将变得更有弹性，盈余最终将开始下降。结果是一个颠倒的J曲线！

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关于Alevel经济笔记第四章：Exchange Rates后续的更新计划如下：