A general rule of efficiency is that an individual or group should specialize in production activities in which it can operate more efficiently than other entities. This principle is referred to as comparative advantage when discussing international trade theory; it states that the worldwide production output is maximized when each country concentrates on producing goods for which it has lower opportunity costs.
Terms of Trade
In Figure 5.1, the U.S. is the low-cost producer for wheat, as it only gives up one unit of steel when it produces one unit of wheat. Great Britain is the high-cost producer for wheat, as it must give up two units of steel for each unit of wheat produced. However, Great Britain is the low cost producer for steel, as it gives up only one-half of a unit of wheat for each unit of steel produced. Therefore, the U.S. has a comparative advantage in producing wheat, while Great Britain has a comparative advantage in producing steel. According to the trade efficiency rule, the world will be better off if Great Britain specializes in steel production and the U.S. specializes in wheat production.
An easy way to determine which country has the comparative advantage is to compare the slopes of the production possibility curves. Suppose you have production possibility curves for two countries with product Y and X, and product Y is placed on the y-axis. The country with the most negative slope for product Y will have the comparative advantage with product Y.
Suppose each country specialized in producing the good for which it had a comparative advantage. The U.S. would produce 50 units of wheat per worker and Great Britain would produce 40 units of steel per worker. The combined world output would be 50 units of wheat and 40 units of steel. With no trade, the combined wheat output is 45 units and the combined steel output is 35 units. Clearly the two countries can benefit from trading with one another - the quantity of wheat produced goes up by five units and the quantity of steel produced goes up by five units. Trading offers more efficient production possibilities.