Ricardian trade
Also known as: Ricardian trade model, theory of comparative advantage
Ricardian trade is the economic model showing that two countries both gain from trade when each specializes in the good it produces at the lower opportunity cost. It is the foundation of the theory of comparative advantage.
Named for the 19th-century economist David Ricardo, the Ricardian model answers a question that seems paradoxical: can a country that is worse at producing everything still benefit from trade? The answer is yes, because what matters is not absolute productivity but opportunity cost — what a country gives up to produce one more unit of a good.
A standard two-country, two-good example makes this concrete. Suppose Country A can produce either 100 units of wheat or 50 units of cloth, while Country B can produce either 40 wheat or 40 cloth. Country A has an absolute advantage in both goods. But in Country A, one unit of cloth costs 2 units of wheat, while in Country B one unit of cloth costs only 1 unit of wheat. Country B therefore has the comparative advantage in cloth, and Country A in wheat. If each specializes and they trade at a rate between the two opportunity costs — say 1.5 wheat per cloth — both end up consuming beyond their own production possibilities curve.
The model explains why trade is generally described as positive-sum rather than a contest one side wins. Its assumptions are deliberately simple: labor is the only input, technology differences drive productivity, and there are constant opportunity costs, so the production possibilities curve is a straight line. Real-world trade adds transport costs, economies of scale, and distributional effects within each country, but the comparative advantage insight survives.
AP Macroeconomics tests this directly. You should be able to compute opportunity costs from an output or input table, identify who holds the absolute and comparative advantage in each good, determine the range of mutually beneficial terms of trade, and show the gains graphically on production possibilities curves.
Key takeaways
- Ricardian trade shows that specialization based on comparative advantage benefits both trading partners.
- Comparative advantage is determined by opportunity cost, not by absolute productivity.
- A country can have an absolute advantage in every good and still gain from trade.
- Trade benefits both parties only when the terms of trade fall between the two countries' opportunity costs.
- AP Macroeconomics asks you to calculate opportunity costs from a table and identify comparative advantage.