The ability to produce a good at lower cost, relative to other goods, compared to another country. In a Ricardian model, comparison is of unit labor requirements; more generally it is of relative autarky prices. With perfect competition and undistorted markets, countries tend to export goods in which they have comparative advantage. A comparative advantage exists when a nation or economic region is able to produce a product at a lower opportunity cost compared to another nation or region. The rule of economics that states: Each country should specialize in producing those goods that it is able to produce relatively most efficiently.