International trade, market structures and impact on the labor market.

Summary This thesis attempts to answer two questions: 1/ To what extent can openness to international trade affect the degree of competition in a market? and 2/ What are the ways in which trade, through its impact on competition, can affect sectoral wages and employment? In the first chapter, we show that trade is associated with strong competition via a high price elasticity of estimated import demand. But when we estimate an index of aggregate concentration (i.e. taking into account both domestic and foreign producers) in chapter 2, we find that it does not decline with foreign penetration in OECD countries. The third chapter, offers the literature a new theoretical and easily testable linear relationship between wages and export market shares. In contrast to the case of Asian and Latin American countries, we find that in OECD and Mediterranean countries an increase in export market share in foreign markets but also in the domestic market is associated with an increase in sectoral wages. Finally, in the last chapter, we argue that the literature has often considered the substitution effect in the study of the trade-employment link. However, we show theoretically and then by means of empirical tests on developed and developing countries that imports and exports have a demand effect, which is always positive for employment. The idea is that openness, by increasing efficiency and/or competition in the market for a good, reduces its equilibrium price, which translates into an increase in its total demand, this effect being beneficial to all actors, domestic and foreign, in the market.