Hideo Konishi

Core in a simple coalition formation game

Abstract. We analyze the core of a class of coalition formation game in which every players payoff depends only on the members of her coalition. We first consider anonymous games and additively separable games. Neither of these strong properties guarantee the existence of a core allocation, even if additional strong properties are imposed. We then introduce two top-coalition properties each of which guarantee the existence. We show that these properties are independent of the Scarf-balancedness condition. Finally we give several economic applications.

Free Trade Networks

The paper examines the formation of free trade agreements (FTAs) as a network formation game. We consider a general n-country model in which countries trade differentiated industrial commodities as well as a numeraire good. Countries may be different in the size of the industrial good industry (measure of firms) and the market size (population size). Their incentives to sign an FTA depend on these characteristics of their own countries and those of their partner countries. We show that if all countries are symmetric, a complete global free trade network is pairwise stable and it is the unique stable network if industrial commodities are not highly substitutable. We also compare FTAs and customs unions (CUs) as to which of these two regimes facilitate global trade liberalization, emphasizing the fact that unlike in the case of a CU, each country signing an FTA can have a new FTA with an outside country without consent of other member countries.

Credible Group-Stability in Many-to-Many Matching Problems

It is known that in two-sided many-to-many matching problems, pairwise stable matchings may not be immune to group deviations, unlike in many- to-one matching problems (Blair 1988). In this paper, we show that pairwise stability is equivalent to credible group stability when one side has responsive preferences and the other side has categorywise- responsive preferences. A credibly group-stable matching is immune to any “executable” group deviations with an appropriate definition of executability. Under the same preference restriction, we also show the equivalence between the set of pairwise-stable matchings and the set of matchings generated by coalition-proof Nash equilibria of an appropriately defined strategic-form game.

The Endogenous Formation of a City: Population Agglomeration and Marketplaces in a Location-Specific Production Economy

Much of the literature on the endogenous generation of a city employs increasing returns to scale in order to obtain agglomeration. In contrast, the model considered here focuses on the role of marketplaces or trading centers in the agglomeration of population as cities. Gains to trade in combination with transportation and marketplace setup costs suffice to endogenously generate a city or cities with one or multiple marketplaces. It is assumed that consumers are fully mobile while production functions are location-specific. The exchange of commodities takes place in competitive markets at the marketplaces, while the number and locations of the marketplaces are determined endogenously using a core concept. Unlike the standard literature of urban economics, our model can deal with differences in geography by letting the setup costs of marketplaces and the transportation system depend on location. After showing that an equilibrium exists and that equilibrium allocations are the same as core allocations, we investigate the equilibrium number and locations of marketplaces, the population distribution, and land prices. In contrast with earlier literature, the results are general in the sense that specific functional forms are not needed to obtain existence of equilibrium, equilibria are first best, and equilibria are locally unique (in our examples).

Endogenous trade policy under foreign direct investment

Abstract Using Bernheim and Whinston (1986) common agency game, we endogenize trade policy in a duopoly composed of a domestic firm and a foreign firm, where both firms influence the domestic governments trade policy via their contributions. The foreign firm can jump over trade restrictions by undertaking foreign direct investment (FDI) in the domestic market. The government prefers a voluntary export restraint (VER) to a tariff for two reasons. First, a VER leads to higher contributions from the foreign firm than a tariff. Second, a VER provides a higher level of protection to the domestic firm without generating FDI by the foreign firm.

Games of Capacity Manipulation in Hospital-intern Markets

In this paper, we analyze capacity manipulation games in hospital-intern markets inspired by the real-life entry-level labor markets for young physicians who seek residencies at hospitals. In a hospital-intern market, the matching is determined by a centralized clearinghouse using the preferences revealed by interns and hospitals and the number of vacant positions revealed by hospitals. We consider a model in which preferences of hospitals and interns are common knowledge. Hospitals play a capacity-reporting game. We analyze the equilibria of the game-form under the two most widely used matching rules: hospital-optimal and intern-optimal stable rules. We show that (i) there may not be a pure strategy equilibrium in general; and (ii) when a pure strategy equilibrium exists, every hospital weakly prefers this equilibrium outcome to the outcome of any larger capacity profile. Finally, we present conditions on preferences to guarantee the existence of pure strategy equilibria.

A Pareto-improving commodity tax reform under a smooth nonlinear income tax

Abstract This paper analyzes the welfare effects of commodity tax reform in an economy with a nonlinear income tax and linear commodity taxes. The main result is that we can find a tax reform program that improves every consumers utility in the Pareto sense unless efficiency loss in the economy is minimized under incentive compatibility. The tax reform rule proposed here applies to a broad class of economies with arbitrary smooth income taxes. The expenditure function approach makes our analyses clear and simple. Some intuition is presented on the role of commodity taxation in a mixed tax economy. The relationship with previous work in optimal tax and tax reform theory is also discussed. We extend our result to the case where the government spends tax revenue to provide a public good.

Migration-proof Tiebout equilibrium: existence and asymptotic efficiency

Tiebouts basic claim was that when public goods are local there is an equilibrium and every equilibrium is efficient. The literature seems fall short of verifying this conjecture: If the notion of equilibrium is too weak then equilibrium is nonempty yet some equilibria could be inefficient. On the other hand, if the notion of equilibrium is too strong, then every equilibrium is efficient yet equilibrium may be empty. This paper introduces a new equilibrium notion, a \textit{migration-proof Tiebout equilibrium}, which is a jurisdiction structure such that (i) no consumer wants to migrate unilaterally across jurisdictions (free mobility of consumers), and (ii) no subgroup of consumers want to form a new jurisdiction that would not create instability in population distribution (free entry of migration-proof jurisdictions). We show that there is always a unique migration-proof equilibrium and is asymptotically efficient when consumers are homogeneous.

Equivalence of strong and coalition-proof Nash equilibria in games without spillovers (*)

This paper examines the conditions which guarantee that the set of coalition-proof Nash equilibria coincides with the set of strong Nash equilibria in the normal form games without spillovers. We find that population monotonicity properties of the payoff functions, when the payoff of a player changes monotonically when the size of the group of players choosing the same strategy increases, are crucial to obtain the equivalence of these two solution concepts. We identify the classes of games, satisfying population monotonicity properties, which yield the equivalence of the set of coalition-proof Nash equilibria and the set of strong Nash equilibria. We also provide sufficient conditions for the equivalence result even when the population monotonicity assumptions are relaxed.

Existence of Stationary Equilibrium in the Markets for New and Used Durable Goods

We prove the existence of stationary equilibrium in the primary and secondhand markets for an indivisible consumer durable in a general model with stochastic degradation and endogenous scrappage decisions.