International Trade and Exchange Rates

Why countries trade

Look at the labels on the things around you, and you will find a map of the world: a phone designed in one country, assembled in another, using parts from a dozen more. International trade lets countries consume a wider variety of goods, at lower prices, than they could produce alone.

The basic reasons for trade are simple:

• Different resources. Some countries have oil, fertile land, or a warm climate; others do not.
• Specialization and scale. Producing large volumes of one thing is often cheaper per unit, so it pays to specialize and trade.
• Variety and competition. Trade gives consumers more choices and puts competitive pressure on domestic firms to improve.

The deepest reason, though, is less obvious, and it is one of the most important ideas in economics.

Comparative advantage

In 1817, the economist David Ricardo showed that two countries can both gain from trade even if one of them is better at producing everything. The key is not absolute ability but opportunity cost: what you give up to produce something.

Imagine two countries that each make cloth and wine. Here is how many hours of work one unit takes:

Country A is faster at both. It has an absolute advantage in everything. But look at opportunity costs:

• In Country A, making one unit of wine takes the time needed for 2 units of cloth. Wine costs 2 cloth.
• In Country B, one unit of wine takes the time needed for half a unit of cloth. Wine costs 0.5 cloth.

Wine is relatively cheap to make in Country B, and cloth is relatively cheap in Country A. Country B has a comparative advantage in wine and Country A in cloth. If each specializes in its comparative advantage and they trade at any price between 0.5 and 2 cloth per wine, both can end up consuming more of both goods than they could alone.

You do not need to be the best at anything to gain from trade. You need to be relatively less bad at something.

The same logic works for people. A surgeon may also be a faster typist than their assistant, but they are better off spending their time on surgery and letting the assistant type.

Trade has winners and losers within countries

Comparative advantage shows that trade makes a country better off in total. It does not say everyone gains. When imports grow, workers and firms in competing industries can lose jobs and income, often concentrated in particular towns and regions. Meanwhile, the gains, lower prices and new export opportunities, are spread widely and are less visible.

This is why trade policy is politically difficult, and why economists often argue for policies that share the gains: retraining, wage insurance, and support for affected regions, rather than blocking trade altogether.

Tools of trade policy

• Tariffs are taxes on imports. They raise the price of foreign goods, protecting domestic producers, but they also raise costs for consumers and for businesses that use imported parts. Other countries often retaliate with their own tariffs.
• Quotas limit the quantity of a good that can be imported.
• Subsidies help domestic producers compete, at taxpayers' expense.
• Trade agreements lower barriers between countries, often with rules on standards, investment, and disputes. The World Trade Organization sets rules for most of world trade.

Trade balances: what a deficit means

A country has a trade deficit when it imports more than it exports, and a trade surplus when it exports more. Trade deficits are often described as a sign of weakness, but the picture is more complicated.

The trade balance is part of the current account, which also includes income from investments abroad and transfers. A current account deficit must be matched by a surplus on the financial account: foreigners are investing in the country, buying its bonds, shares, property, or companies. In other words, a country that imports more than it exports is financing the difference by selling assets or borrowing from abroad.

Underneath, the trade balance reflects saving and investment:

A country that invests more than it saves must import the difference in capital from abroad, and that shows up as a current account deficit. This is why trade deficits often widen in booms, when investment and spending are strong, and narrow in recessions. A deficit can be healthy, if it finances productive investment, or worrying, if it finances consumption that cannot be sustained and relies on foreign lenders who might leave.

Exchange rates

To trade across borders, money has to be converted. The exchange rate is the price of one currency in terms of another. If 1 U.S. dollar buys 0.90 euros, the euro price of a dollar is 0.90, and the dollar price of a euro is about 1.11.

• When a currency appreciates, it buys more foreign currency. Imports get cheaper for that country, and its exports get more expensive for foreigners.
• When a currency depreciates, the reverse happens: exports become more competitive, and imports, and foreign travel, cost more.

Floating and fixed rates

Most major currencies, including the U.S. dollar, euro, Japanese yen, and British pound, float: their value is set by supply and demand in currency markets. Some countries peg their currency to another, usually the dollar or euro, and use their central bank's reserves to defend the rate. A peg brings stability for trade but ties the country's interest rates to the anchor currency and can collapse if markets doubt it.

What moves exchange rates

• Interest rates. Higher interest rates attract foreign investors seeking better returns, raising demand for the currency. This is one channel through which central bank decisions affect trade.
• Inflation. Over the long run, countries with higher inflation tend to see their currencies depreciate.
• Growth and investment opportunities. A strong, growing economy attracts capital.
• Risk and safe havens. In global crises, investors often buy dollars, Swiss francs, or yen, which strengthens them.
• Trade flows. Strong demand for a country's exports raises demand for its currency.
• Expectations and speculation, which can move rates sharply in the short run.

Purchasing power parity

The theory of purchasing power parity (PPP) says that in the long run, exchange rates should move so that the same basket of goods costs the same in different countries. The Economist's Big Mac Index is a playful version of this idea: comparing the price of a Big Mac across countries suggests which currencies look overvalued or undervalued. In practice, exchange rates can stay far from PPP for years, because many goods and services, like haircuts and housing, are not traded internationally.

Why it matters to you

Trade and exchange rates reach into everyday life:

• A weaker home currency makes imported goods, foreign holidays, and imported energy more expensive, and can add to inflation.
• A stronger currency makes travel abroad cheaper but can hurt exporters and the people they employ.
• Investments in foreign stocks or bonds rise or fall with exchange rates as well as with their own prices.
• Tariffs can raise prices on everyday goods, even when they are aimed at foreign producers.

Key ideas to remember

• Countries trade to access different resources, gain from specialization, and increase variety.
• Comparative advantage, based on opportunity cost, means both sides can gain even when one is better at everything.
• Trade raises total income but creates losers in exposed industries, which is a major reason trade policy is contested.
• A trade deficit is matched by foreign investment and reflects saving and investment, not simply weakness.
• Exchange rates respond to interest rates, inflation, growth, risk, and expectations; appreciation makes imports cheaper and exports dearer.