What is the primary gain from international trade?

Answer 1

In theoretical economics, for gains from trade we distinguish between

(a) A small country trading with RoW (Rest of the World), where the former is a price taker and cannot influence world prices, the maximum it can do is exchange at world prices. For a closed small economy by opening up to trade and partially specialise in its comparative advantage (cost advantage) helps to exchange more of the non-comparative advantage commodity from the world, thus taking the country to a higher utility schedule. Ex: For a production of clothing and food, say small country has a comparative advantage in food production, while the Row in clothing, thus small country can choose to produce food which it can more efficiently and then exchange it for clothing from RoW. Thus for a small country consumer more of both is available, raising utility.

(b) A large country trading with RoW, here the large country is a monopolist concerned with supply, and also affects world demand with its large demand for imports, hence a monopolist would choose not to operate at (a) P=MC and (b) remain on the inelastic part of the demand curve and hence resorting to an optimal tariff bound trade that takes it to the maximum utility. This is easy to understand and involves a derivation, but this is the essential introduction.