Ricardo's Comparative Advantage

David Ricardo solved Smith's puzzle in 1817. In his famous example, Portugal could produce both wine and cloth with less labor than England, so it had an absolute advantage in both. Yet Portugal's advantage was greater in wine, while England's disadvantage was smallest in cloth. If each specialized according to this comparative advantage, the lower opportunity cost, and traded, both countries could end up with more of both goods.

The key insight is that trade depends on relative, not absolute, efficiency: even a less productive country has something it gives up less to make. Comparative advantage became one of the most important ideas in economics, but it rests on assumptions, such as workers moving easily between industries and full employment, that do not always hold. Critics also note that in Ricardo's era Portugal's specialization in wine reflected an unequal treaty relationship with Britain, a reminder that real trade patterns also reflect power.