We have now developed the simplest of all models of international trade. Even though the ricardian one – factor model is far too simple to be a complete analysis of either the causes or the effects if international trade, a focus on relative labor productivities can be a very useful tool for thinking about international trade. In particular, the simple one – factor model is a good way to deal with several common misconceptions about the meaning of comparative advantage and the nature of the gains from trade. These misconceptions appear so frequently in public debate about international economic policy, and even in statements by those who regard themselves as experts, that in the next section we take time out to discuss some of the most common misunderstandings about comparative advantage in light of our model.