This paper investigates how horizontal mergers affect the optimal entry barrier (tax) in the presence of free entry and exit. We show that the government should raise the entry tax when a merger reduces the total number of firms entering.

In linear-city models, if firms are allowed (not allowed) to locate outside the linear city, they engage in excessive (insufficient) R&D investments from the normative viewpoint. This implies that the feasible set of locations drastically affects their investments.

This paper introduces a local version of envy-freeness and investigates its implications in a continuum agent economy with connected preferences. We show that the set of locally envy-free and Pareto efficient allocations coincides with the set of equal-income Walrasian allocations.

This paper is concerned with the problem of extending an antisymmetric binary relation on a set to a linear order on the power set. A necessary and sufficient condition is offered.

This paper examines the logical relationship among Maskin monotonicity, independent person-by-person monotonicity, independent weak monotonicity, strategy-proofness, and coalitional strategy-proofness in a society with infinite individuals.

This paper provides an alternative proof of the Gibbard-Satterthwaite theorem.

We revisit the classic discussion of the endogenous choice of a price or a quantity contract, but in a mixed duopoly. We find that choosing the price contract is a dominant strategy for both firms, whether the goods are substitutes or complements.