Because of comparative advantage, trade raises the living standards of both countries. Douglas Irwin (2009) calls comparative advantage “good news” for economic development. “Even if a developing country lacks an absolute advantage in any field, it will always have a comparative advantage in the production of some goods,” and will trade profitably with advanced economies.

Differences in comparative advantage may arise for several reasons. In the early 20th century, Swedish economists Eli Heckscher and Bertil Ohlin identified the role of labour and capital, so-called factor endowments, as a determinant of advantage. The Heckscher-Ohlin proposition maintains that countries tend to export goods whose production uses intensively the factor of production that is relatively abundant in the country. Countries well endowed with capital—such as factories and machinery—should export capital-intensive products, while those well endowed with labour should export labour-intensive products. Economists today think that factor endowments matter, but that there are also other important influences on trade patterns (Baldwin, 2008).

Recent research finds that episodes of trade opening are followed by adjustment not only across industries, but within them as well. The increase in competition coming from foreign firms puts pressure on profits, forcing less efficient firms to contract and making room for more efficient firms. Expansion and new entry bring with them better technologies and new product varieties. Likely the most important is that trade enables greater selection across different types of goods (say refrigerators). This explains why there is a lot of intra-industry trade (for example, countries that export household refrigerators may import industrial coolers), which is something that the factor endowment approach does not encompass.