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Trade and Comparative Advantage ch3

Sep 8, 2025

Overview

This lecture discusses the reasons for trade, introduces the concepts of absolute and comparative advantage, and uses a model to show how countries can gain from specializing and trading.

Why Trade Makes Sense

  • Trade allows people and countries to consume more than they could produce on their own.
  • Two-country model: U.S. and Japan each produce only computers and tomatoes, using only labor.
  • Without trade, each country consumes only what it produces, limited by labor resources.

Exports and Imports

  • An export is a good produced domestically and sold abroad.
  • An import is a good produced abroad and sold domestically.

Effects of Trade on Consumption

  • With trade, the U.S. exports tomatoes and imports computers; Japan does the opposite.
  • After trading, both countries can consume combinations of goods outside their production possibility frontier (PPF), meaning higher consumption than possible when self-sufficient.
  • For example, U.S. can consume more computers and tomatoes after trade than before; the same is true for Japan.

Gains from Trade

  • Both countries are better off after trade, though the gains do not need to be equal.
  • The important factor is that each country is better off compared to not trading.

Specialization and Advantage

  • Countries gain from specializing in goods they produce more efficiently and trading for those they do not.
  • The analysis depends on understanding different types of advantage.

Absolute vs. Comparative Advantage

  • Absolute advantage: producing a good using fewer resources (lower cost) than another country.
  • In the example, the U.S. has an absolute advantage in tomato production (uses fewer labor hours per ton).
  • Gains from trade depend more on comparative advantage (lowest opportunity cost), not just absolute advantage.

Key Terms & Definitions

  • Production Possibility Frontier (PPF) — the combinations of goods a country can produce given its resources and technology.
  • Export — a good produced domestically and sold abroad.
  • Import — a good produced abroad and sold domestically.
  • Absolute Advantage — the ability to produce a good with fewer resources than another producer.
  • Comparative Advantage — the ability to produce a good at a lower opportunity cost than another producer.
  • Opportunity Cost — the value of the next-best alternative given up when making a choice.

Action Items / Next Steps

  • Review the concepts of absolute and comparative advantage.
  • Prepare for the next lecture on comparative advantage and opportunity cost.