Why are increasing returns to scale and fixed costs important in models of international trade and imperfect competition?

Question

What will be an ideal response?

Answer 1

There are many answers. Three of these are
(a) Increasing returns to scale and high fixed costs may be inconsistent with perfect competition. In such a case, the initial autarkic state may be a suboptimal equilibrium. For example, relative prices may not equal marginal rates of transformation. It follows from this that a change in output compositions associated with trade may result in a national welfare for one or both trading countries that is inferior to that associated with the initial autarkic conditions. Hence no "gains from trade."
(b) In a case of increasing scale economies at the firm or plant level, the determination of which product will be exported by which country is ex-ante indeterminate. Therefore, deriving clear implications concerning the effects of trade on income distributions such as may be derived from the Samuelson-Stolper Theorem is no longer generally possible.
(c) Market structures containing positive scale economies and imperfect competition may allow for "two-way trade," or intra-industry trade. As in b. above, the various theorems derivable from the Heckscher-Ohlin model concerning directions of trade and income distributions are no longer generally applicable.