要旨：In this paper, I construct a two-country general equilibrium model in which oligopolistic firms export goods and undertake cost-reducing R&D investment. Each country imposes tariffs. When the cost of education is sufficiently high, an increase in the tariff rate decreases the level of R&D investment. On the other hand, when the cost of education is sufficiently small, an increase in the tariff rate increases the level of R&D investment.

要旨：This paper analyzes the locations of heterogeneous firms, which are differentiated by indices in the industrial space, when communication externalities generate agglomeration economies. The benefit of a communication decreases as the industrial distance between two firms increases. An interregional communication requires travel cost while an intraregional communication requires no cost. There are also agglomeration diseconomies arising from rise in regional wage rate. We derive three types of stable equilibrium configurations: agglomeration, partial agglomeration, and dispersion. Multiple equilibria of agglomeration and dispersion may exist. Agglomeration is likely to occur when the degree of communication intensity and travel cost are large.

要旨：We examine network formation via bilateral trade agreement (BTA) among three symmetric countries. Each government decides the conclusion of a BTA depending on the differential of ex-post and ex-ante simple sum of real wages in the country. We model the governmental decision in two forms, myopic and farsighted and analyze the effects on the BTA network formation. Firstly, both myopic game and farsighted game never induce star networks as well as the empty network. Second, in most of the cases, the networks resulting from the myopic game coincide those resulting from the farsighted game, but there exist some cases where the two games yield distinct networks.