Understanding International Trade
International trade was key to the rise of the global economy. In the global economy, supply and demand—and thus prices—both impact and are impacted by global events.

Political change in Asia, for example, could result in an increase in the cost of labor. This could increase the manufacturing costs for an American sneaker company that is based in Malaysia, which would then result in an increase in the price charged for a pair of sneakers that an American consumer might purchase at their local mall.

Imports and Exports
A product that is sold to the global market is called an export, and a product that is bought from the global market is an import. Imports and exports are accounted for in the current account section of a country’s balance of payments.

Global trade allows wealthy countries to use their resources—for example, labor, technology, or capital—more efficiently. Different countries are endowed with different assets and natural resources: land, labor, capital, technology, etc.

This allows some countries to produce the same good more efficiently; in other words, more quickly and at a lower cost. Therefore, they may sell it more cheaply than other countries. If a country cannot efficiently produce an item, it can obtain it by trading with another country that can. This is known as specialization in international trade.

Comparative Advantage
For example, England and Portugal have historically been used, as far back as in Adam Smith’s The Wealth of Nations, to illustrate how two countries can mutually benefit by specializing and trading according to their own comparative advantages.1 In such examples, Portugal is said to have plentiful vineyards and can make wine at a low cost, while England is able to more cheaply manufacture cloth given its pastures are full of sheep.2

According to the theory of comparative advantage, each country would eventually recognize these facts and stop attempting to make the product that was more costly to generate domestically in favor of engaging in trade. Indeed, over time, England would likely stop producing wine, and Portugal stop manufacturing cloth. Both countries would realize that it was to their advantage to redirect their efforts at producing what they were relatively better at domestically and, instead, to trade with each other in order to acquire the other.

These two countries realized that they could produce more by focusing on those products for which they have a comparative advantage. In such a case, the Portuguese would begin to produce only wine, and the English only cotton.

Each country can now create a specialized output of 20 units per year and trade equal proportions of both products. As such, each country now has access to both products at lower costs. We can see then that for both countries, the opportunity cost of producing both products is greater than the cost of specializing.

Comparative advantage can contrast with absolute advantage. Absolute advantage leads to unambiguous gains from specialization and trade only in cases wherein each producer has an absolute advantage in producing some good.

If a producer lacked any absolute advantage, then they would never export anything. But we do see that countries without any clear absolute advantage do gain from trade because they have a comparative advantage.

 According to international trade theory, even if a country has an absolute advantage over another, it can still benefit from specialization.
Origins of Comparative Advantage
The theory of comparative advantage has been attributed to the English political economist David Ricardo. Comparative advantage is discussed in Ricardo’s book On the Principles of Political Economy and Taxation, published in 1817, although it has been suggested that Ricardo’s mentor, James Mill, likely originated the analysis and slipped it into Ricardo’s book on the sly.345

Comparative advantage, as we have shown above, famously showed how England and Portugal both benefit by specializing and trading according to their comparative advantages. In this case, Portugal was able to make wine at a low cost, while England was able to cheaply manufacture cloth. Ricardo predicted that each country would eventually recognize these facts and stop attempting to make the product that was more costly to generate.5

A more contemporary example of comparative advantage is China’s comparative advantage over the United States in the form of cheap labor. Chinese workers produce simple consumer goods at a much lower opportunity cost.6

The comparative advantage for the U.S. is in specialized, capital-intensive labor. American workers produce sophisticated goods or investment opportunities at lower opportunity costs. Specializing and trading along these lines benefit each country.

The theory of comparative advantage helps to explain why protectionism has been traditionally unsuccessful. If a country removes itself from an international trade agreement, or if a government imposes tariffs, it may produce an immediate local benefit in the form of new jobs; however, this is rarely a long-term solution to a trade problem.

Eventually, that country will grow to be at a disadvantage relative to its neighbors: countries that were already better able to produce these items at a lower opportunity cost.