Gains from trade can be realized anytime a comparative advantage exists so long as the potential trading partners are willing to specialize in the activities in which they enjoy a comparative advantage. As we will see, comparative advantages almost always exist.

Though comparative advantages almost always exist, guaranteeing that specialization and trade will yield gains from trade, the size of these gains will depend on the terms of trade agreed upon by the trading partners, and the amount of trading in which they engage. We will see that, though economics will not allow us to predict precisely what terms of trade will be agreed upon, we can determine the range of possible terms of trade.