📚 Exchange Rates: Definitions & Measurement Explained | 汇率的定义与衡量方法详解
An exchange rate is the price of one currency expressed in terms of another currency. It is one of the most important variables in an open economy because it affects trade flows, capital movements, inflation and the overall competitiveness of a country's producers.
汇率是一种货币以另一种货币表示的价格。在开放经济中，汇率是最重要的经济变量之一，因为它会影响贸易流动、资本流动、通货膨胀以及一国生产者的整体竞争力。
1. What Is an Exchange Rate? | 什么是汇率？
An exchange rate tells us how many units of one currency must be given up to obtain one unit of another currency. For example, if the exchange rate between the US dollar and the British pound is 1 USD = 0.78 GBP, then one US dollar can be traded for 0.78 British pounds.
汇率告诉我们，要获得一单位另一种货币，需要放弃多少单位的一种货币。例如，如果美元与英镑之间的汇率是 1 美元 = 0.78 英镑，那么一美元可以兑换 0.78 英镑。
In economics, the exchange rate is not simply a number on a screen. It is a relative price that adjusts to balance supply and demand in the foreign exchange market. When a currency becomes more valuable relative to another, its exchange rate rises; when it becomes less valuable, its exchange rate falls.
在经济学中，汇率不仅仅是屏幕上的一个数字。它是一种相对价格，通过外汇市场上的供求关系进行调整。当一种货币相对另一种货币变得更值钱时，其汇率上升；当它变得更不值钱时，其汇率下降。
For A-Level economics, students need to distinguish clearly between nominal, effective and real exchange rates, because each measure answers a different question about a currency's value.
在 A-Level 经济学中，学生需要清楚区分名义汇率、有效汇率和实际汇率，因为每一种衡量方式回答的是关于货币价值的不同问题。
2. Nominal Exchange Rate: Direct vs Indirect Quotation | 名义汇率：直接标价与间接标价
The nominal exchange rate is the most basic measure of the exchange rate. It is simply the rate at which one currency is traded for another in the foreign exchange market.
名义汇率是最基本的汇率衡量方式。它只是外汇市场中一种货币与另一种货币交易的比率。
There are two common ways to quote a nominal exchange rate. A direct quote expresses the price of one unit of foreign currency in terms of domestic currency. An indirect quote expresses the price of one unit of domestic currency in terms of foreign currency.
名义汇率有两种常见的报价方式。直接标价法是以本国货币来表示一单位外国货币的价格；间接标价法是以外国货币来表示一单位本国货币的价格。
| Quotation Type | Example | Meaning |
| Direct quote | 1 GBP = 1.60 USD | One pound costs 1.60 dollars |
| Indirect quote | 1 USD = 0.625 GBP | One dollar costs 0.625 pounds |
In the table above, the direct and indirect quotations are simply reciprocal ways of expressing the same relative price. A fall in the direct quote means that the domestic currency has appreciated because one unit of foreign currency now buys fewer units of domestic currency.
在上表中，直接标价和间接标价只是同一相对价格的互为倒数的表达方式。直接标价下降意味着本币升值，因为一单位外国货币现在能买到的本国货币变少了。
Nominal exchange rate (direct) = units of domestic currency ÷ 1 unit of foreign currency
Nominal exchange rates are the rates quoted in newspapers, banks and trading platforms. However, they only compare two currencies at a time and do not tell us whether a currency is gaining or losing purchasing power at home.
名义汇率是报纸、银行和交易平台上所报出的汇率。然而，它每次只比较两种货币，并不能告诉我们一种货币在国内的购买力是在上升还是下降。
3. Appreciation and Depreciation | 升值与贬值
When the value of a currency rises under a floating exchange rate system, the currency is said to appreciate. When its value falls, the currency is said to depreciate.
在浮动汇率制度下，当一种货币的价值上升时，我们称该货币升值；当它的价值下降时，我们称该货币贬值。
For example, suppose the exchange rate changes from 1 GBP = 1.40 USD to 1 GBP = 1.50 USD. The pound has appreciated against the dollar because one pound now buys more dollars.
例如，假设汇率从 1 英镑 = 1.40 美元变为 1 英镑 = 1.50 美元。英镑兑美元升值了，因为一英镑现在能兑换更多美元。
Appreciation and depreciation are relative concepts. A currency can appreciate against one currency while depreciating against another during the same period. This is why economists need a broader measure of the currency's overall external value.
升值和贬值是相对概念。在同一时期内，一种货币可能对某一种货币升值，同时对另一种货币贬值。这就是为什么经济学家需要一种更广泛的指标来衡量货币的整体对外价值。
Appreciation: an increase in the market value of a currency under floating rates.
升值：在浮动汇率制下，一种货币市场价值的上升。
Depreciation: a decrease in the market value of a currency under floating rates.
贬值：在浮动汇率制下，一种货币市场价值的下降。
4. Bilateral vs Effective Exchange Rate | 双边汇率与有效汇率
A bilateral exchange rate is the rate between two currencies, such as the pound against the dollar or the pound against the euro. It is useful for comparing two countries directly, but it gives an incomplete picture of overall competitiveness.
双边汇率是两种货币之间的汇率，例如英镑兑美元或英镑兑欧元。它有助于直接比较两个国家，但无法完整反映整体竞争力。
The effective exchange rate is a weighted average of a country's currency against a basket of other currencies. Because countries trade with many partners, the effective exchange rate is a better indicator of the average external value of the currency.
有效汇率是一国货币对一篮子其他货币的加权平均值。由于一个国家与许多贸易伙伴进行贸易，有效汇率是衡量货币平均对外价值的更好指标。
For example, if the pound rises sharply against the dollar but falls against the euro, the bilateral pound-dollar rate will show an appreciation while the bilateral pound-euro rate will show a depreciation. The effective exchange rate combines both movements according to the importance of each trading partner.
例如，如果英镑兑美元大幅上升，但兑欧元下跌，那么英镑兑美元的双边汇率显示升值，而英镑兑欧元的双边汇率显示贬值。有效汇率会根据每个贸易伙伴的重要性，将这两种变动结合起来。
In CIE A-Level economics, the effective exchange rate is often referred to as the trade-weighted exchange rate. It is essential for measuring competitiveness over time.
在 CIE A-Level 经济学中，有效汇率通常被称为贸易加权汇率。它在衡量长期竞争力时至关重要。
5. How the Effective Exchange Rate Is Measured | 有效汇率的衡量方法
The effective exchange rate is measured by selecting a base year and calculating an index for each bilateral exchange rate. Then each currency is given a weight based on its share in the country's international trade.
衡量有效汇率时，首先要选择一个基期年份，并计算各双边汇率的指数。然后，根据每个贸易伙伴在国际贸易中所占的份额，给予每种货币一个权重。
The index formula can be written as:
有效汇率指数公式如下：
EER = (w₁ × I₁) + (w₂ × I₂) + ... + (wₙ × Iₙ)
Here, w represents the trade weight for each partner country and I represents the bilateral exchange rate index for that partner. The weights should add up to 1, or 100 percent.
其中，w 代表每个贸易伙伴国家的贸易权重，I 代表与这个伙伴国家的双边汇率指数。各权重之和应等于 1，即 100%。
| Trading Partner | Trade Weight | Exchange Rate Index |
| Country A | 0.50 | 110 |
| Country B | 0.30 | 95 |
| Country C | 0.20 | 100 |
Using the table, the effective exchange rate index would be:
根据上表，有效汇率指数为：
EER = (0.50 × 110) + (0.30 × 95) + (0.20 × 100) = 55 + 28.5 + 20 = 103.5
An index above 100 means the currency has appreciated on a trade-weighted basis compared with the base year. An index below 100 means it has depreciated.
指数高于 100，意味着与基期相比，该货币在贸易加权基础上升值了。指数低于 100，则意味着它贬值了。
6. Real Exchange Rate: Concept and Formula | 实际汇率：概念与公式
The nominal exchange rate is measured in money terms, but it does not account for differences in price levels between countries. The real exchange rate adjusts the nominal rate for relative inflation.
名义汇率以货币形式衡量，但没有考虑各国之间价格水平的差异。实际汇率则根据相对通货膨胀对名义汇率进行调整。
The real exchange rate is defined as the nominal exchange rate multiplied by the ratio of foreign prices to domestic prices. Let E be the nominal exchange rate measured as units of domestic currency per unit of foreign currency.
实际汇率定义为名义汇率乘以外国价格与国内价格之比。设 E 为以本国货币表示一单位外国货币的名义汇率。
Real exchange rate (RER) = (E × P*) ÷ P
In this formula, P* is the foreign price level and P is the domestic price level. The real exchange rate is therefore a relative price: it compares how much of a basket of domestic goods must be sacrificed to obtain a basket of foreign goods.
在这个公式中，P* 是外国价格水平，P 是国内价格水平。因此，实际汇率是一种相对价格：它比较的是为获得一篮子外国商品，需要放弃多少一篮子本国商品。
Alternatively, using natural units, the real exchange rate can be seen as the terms of trade between two countries' output. A higher real exchange rate suggests that foreign goods are becoming more expensive relative to domestic goods.
或者，用实际单位来看，实际汇率可以视为两国产出之间的贸易条件。实际汇率上升，表明外国商品相对于本国商品变得更昂贵。
7. Interpreting Real Exchange Rate Changes | 解读实际汇率变动
If the real exchange rate rises, it means foreign goods have become relatively more expensive compared with domestic goods. This is equivalent to a real depreciation of the domestic currency, even if the nominal rate has not changed.
如果实际汇率上升，意味着外国商品相对本国商品变得更贵。这相当于本币发生了实际贬值，即使名义汇率没有变化。
If the real exchange rate falls, domestic goods have become relatively more expensive. This is a real appreciation, and it tends to reduce net exports because domestic goods lose competitiveness abroad.
如果实际汇率下降，本国商品相对变得更贵。这就是实际升值，它往往会减少净出口，因为本国商品在国外的竞争力下降。
Real exchange rate changes can occur even when the nominal exchange rate is fixed. If a country has higher inflation than its trading partners, its real exchange rate will rise and its goods will become less competitive.
即使名义汇率固定不变，实际汇率也可能发生变化。如果一国通货膨胀率高于其贸易伙伴国，其实际汇率就会上升，商品竞争力就会下降。
This is a key distinction for A-Level students: nominal movements show what happens in the foreign exchange market, while real movements show what happens to a country's international competitiveness.
这是 A-Level 学生需要理解的关键区别：名义变动反映外汇市场上的变化，而实际变动反映一国国际竞争力的变化。
8. Methods of Measuring Exchange Rates in Practice | 实践中汇率的衡量方法
In practice, exchange rates are measured using different market labels. The spot exchange rate is the rate for immediate delivery of currency, usually within two business days. It is the current market price.
在实践中，汇率用不同的市场术语来衡量。即期汇率是用于立即交割货币的汇率，通常是在两个工作日内。它就是当前市场价格。
The forward exchange rate is an agreed rate for a currency exchange to take place on a specified future date. Businesses use forward rates to reduce uncertainty about future currency movements.
远期汇率是双方约定的、在未来某一特定日期进行货币兑换的汇率。企业利用远期汇率来减少未来汇率变动的不确定性。
The official exchange rate is set by a central bank or government, usually in fixed or managed exchange rate systems. The market exchange rate is determined by demand and supply in the foreign exchange market.
官方汇率是由中央银行或政府设定的汇率，通常存在于固定汇率制或管理汇率制中。市场汇率则由外汇市场中的供求关系决定。
Spot rate: current market rate for immediate delivery.
即期汇率：用于立即交割的当前市场汇率。
Forward rate: agreed rate for future delivery.
远期汇率：用于未来交割的约定汇率。
Official rate: set by the monetary authority.
官方汇率：由货币当局设定的汇率。
Market rate: determined by demand and supply.
市场汇率：由供求关系决定的汇率。
For analytical purposes, index numbers are more useful than raw exchange rates because they allow economists to compare changes over time against a consistent base year.
对于分析而言，指数比原始汇率更有用，因为它允许经济学家以一致的基期年份比较不同时期的变化。
9. Factors Influencing Exchange Rate Measurement | 影响汇率衡量的因素
The measured value of an exchange rate depends heavily on how it is constructed. Different base years, different currency baskets and different weighting systems can produce very different pictures of the same currency.
汇率的测量值在很大程度上取决于其构建方式。不同的基期年份、不同的货币篮子以及不同的加权体系，可能会对同一种货币产生非常不同的图景。
Trade weights can be measured using merchandise trade only, or they can include services and capital flows. The choice affects the effective exchange rate index.
贸易权重可以只按商品贸易衡量，也可以将服务贸易和资本流动纳入其中。这一选择会影响有效汇率指数。
Data on exchange rates may also be taken from daily closing values, monthly averages or annual averages. Short-term volatility can make a single observation misleading.
汇率数据也可以取自每日收盘价、月平均值或年平均值。短期波动可能使单一观测值产生误导。
In addition, the real exchange rate depends on the price index chosen. The consumer price index is commonly used, but producer price indices may be more appropriate when measuring export competitiveness.
此外，实际汇率取决于所选择的价格指数。消费者价格指数是常用指标，但在衡量出口竞争力时，生产者价格指数可能更合适。
Finally, exchange rate regimes matter. In a fixed system the nominal exchange rate may be constant, but the real exchange rate can still move through inflation differentials.
最后，汇率制度也很重要。在固定汇率制下，名义汇率可能保持不变，但实际汇率仍会通过通胀差异而变动。
10. Exchange Rate Systems and Measurement Context | 汇率制度与衡量背景
Under a floating exchange rate system, the nominal exchange rate is determined by market forces without direct government intervention. Measurement of appreciation and depreciation is straightforward because the market rate changes freely.
在浮动汇率制度下，名义汇率由市场力量决定，政府不直接干预。升值与贬值的衡量较为直接，因为市场汇率可以自由变动。
Under a fixed exchange rate system, the central bank commits to maintain the exchange rate within a narrow band. The official pegged rate may remain constant for many years, even if the equilibrium market rate is different.
在固定汇率制度下，中央银行承诺将汇率维持在较窄的区间内。官方钉住汇率可能在许多年里保持不变，即使市场均衡汇率已经不同。
A managed float combines elements of both systems. The market determines the exchange rate over time, but the central bank may intervene to smooth excessive volatility.
有管理的浮动汇率制结合了两种制度的特点。市场在长期中决定汇率水平，但中央银行可能会进行干预，以平抑过度的波动。
Regardless of the system, economists must measure both nominal and real exchange rates because households, firms and policymakers respond to different aspects of currency movements.
无论采用何种制度，经济学家都必须同时衡量名义汇率和实际汇率，因为家庭、企业和政策制定者会对汇率变动的不同方面作出反应。
11. Conclusion | 总结
The exchange rate is a relative price that can be measured in several ways. The nominal exchange rate tells us the price of one currency in terms of another, while the effective exchange rate gives a trade-weighted average against many currencies.
汇率是一种相对价格，可以通过多种方式衡量。名义汇率告诉我们一种货币以另一种货币表示的价格，而有效汇率则提供了一种货币对多种货币的贸易加权平均值。
The real exchange rate is even more important for competitiveness because it adjusts the nominal rate for price differences between countries. A country's external position depends not only on what happens in currency markets but also on what is happening to relative inflation and productivity.
实际汇率对竞争力更为重要，因为它根据国家之间的价格差异对名义汇率进行了调整。一个国家的对外状况不仅取决于外汇市场的变化，还取决于相对通胀和生产率的变化。
For CIE A-Level economics, you should be able to explain the difference between bilateral and effective rates, calculate a simple effective exchange rate index, and interpret changes in the real exchange rate. Mastery of these definitions and measurement methods is essential for analysing exchange rate policy.
对于 CIE A-Level 经济学，你应该能够解释双边汇率与有效汇率之间的区别，计算简单的有效汇率指数，并解读实际汇率的变动。掌握这些定义和衡量方法，是分析汇率政策的关键。
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