Stability and Segregation in Group Formation

This paper presents a model of group formation based on the assumption that individuals prefer to associate with people similar to them. It is shown that, in general, if the number of groups that can be formed is bounded, then a stable partition of the society into groups may not exist. (A partition is defined as stable if none of the individuals would prefer be in a different group than the one he is in.) However, if individuals' characteristics are one-dimensional, then a stable partition always exists. We give sufficient conditions for stable partitions to be segregating (in the sense that, for example, low-characteristic individuals are in one group and high-characteristic ones are in another) and Pareto efficient. In addition, we propose a dynamic model of individual myopic behavior describing the evolution of group formation to an eventual stable, segregating, and Pareto efficient partition. Journal of Economic Literature Classification Numbers: C72, H41.     

ARAB-ISRAELI POTENTIAL TRADE: THE ROLE OF INPUT SHARING

In this article we sought to develop a methodology for estimating the level and composition of potential trade between Israel and its Arab neighbors. The need for such a methodology derives from the fact that the existing trade of these countries with the rest of the world constitutes an insufficient basis for predicting bilateral trade patterns between them. Trade based on input sharing can be an important source of ''new trade'' that is, trade that is not necessarily related to goods and services currently traded by the countries in question. New trade based on input sharing pertains to the imports by Arab countries of inputs in which Israel has a proven comparative advantage, and to imports by Israel of inputs produced in Arab countries in which the latter have a proven comparative advantage. It stands to reason that branches characterized by comparative advantage in the exporting country can improve the competitive position of the import ing country, when incorporated in the latter's final products. The analysis confirms that in agricultural produce, food products, and certain sub-branches of the textiles and clothing industry, Jordan, Syria, and Egypt all appear to be potential suppliers to Israel. Inter alia, the results show that the Israeli import potential of inputs from Jordan appears to be both larger and more evenly distributed among the different branches than the import potential from Syria and even from Egypt. This finding does not accord with expectations in view of the fact that Jordan has a smaller population and a lower gross domestic product than either Egypt or Syria. Jordan stands out in that its construction industry, including ceramic products, nonmetallic minerals, and structural metals, are also potential suppliers. The methodology developed in this article specifically concerns potential trade between Israel and its Arab neighbors. It can be usefully employed in other situations where trade between pairs of countries is either nonexistent or severely distorted by political or other factors. Examples which come to mind include trade between countries which in the past belonged to the Soviet bloc, or trade between these countries and the rest of the world. In such cases it is improper to base one's trade predictions on the countries' existing trading patterns. New trade, which can be very substantial, and which may have a very different composition from current trade of the parties concerned, must be added to the equation. The methodology demonstrated in this article can be easily adapted for this purpose.     

Sales demands on securities brokers

Measurement and prediction of salesmen's performance are perennial interests of marketing researchers [1, 5, 6]. The question of the criteria used to evaluate salesmen and the relationship between these criteria and the salesmen's career cycle, however, has yet to be systematically analyzed [4, 10]. The salesman's role includes several tasks, some of which impose conflicting demands upon him. This article explores the implications of conflicting demands on the performance of the role of a salesman, and considers their affect on his career path.     

Efficient Sorting in a Dynamic Adverse-Selection Model

We discuss a class of markets for durable goods where efficiency (or approximate efficiency) is obtained despite the presence of information asymmetries. In the model, the number of times a good has changed hands (the vintage of the good) is an accurate signal of its quality, each consumer self-selects into obtaining the vintage that the social planner would have assigned to her, and consumers' equilibrium trading behaviour in secondary markets is not subject to adverse selection. We show that producers have the incentive to choose contracts that lead to the efficient allocation, and to supply the efficient output. We also provide a contrast between leasing contracts, resale contracts, and different kinds of rental contracts. Resale contracts do not lead to the efficient allocation. A specific kind of rental contract provides the appropriate incentives to consumers.     

Local dimensions of global investment: Israeli property firms in Central Europe

Transnational property investment has increased dramatically during the last few decades. This process has been traced by literature focusing on capital‐rich countries (e.g. the United States, Canada, Japan) and on major world cities. More recently, in tandem with the collapse of the Berlin Wall, the geographical horizons of foreign investors have broadened to include former socialist countries. This article examines the recent surge in Israeli property investment in Central Europe and argues that global flows depend on relationships between place of origin and destination. Mobility of property capital creates networks that connect cities on a transnational basis. Les investissements immobiliers transnationaux ont énormément augmenté au cours des dernières décennies. Cet aspect a été suivi et documenté surtout pour les pays riches en capitaux (Etats‐Unis, Canada, Japon, par exemple) et les grandes villes mondiales. Plus récemment, parallèlement à la chute du Mur de Berlin, les horizons géographiques des investisseurs étrangers se sont élargis aux anciens pays socialistes. L'article examine l'afflux récent d'investissements immobiliers israéliens en Europe centrale, affirmant que les flux planétaires dépendent des relations entre les lieux d'origine et de destination. La mobilité des capitaux immobiliers crée des réseaux qui relient des villes au plan transnational.     

Auctions with a random number of identical bidders

We examine and compare the (normally, mixed) symmetric equilibrium bidding strategies in first-price and all-pay common value multiple item auctions with a random number of bidders, who only seek one of the identical items and have the same budget.     

Network topology and the efficiency of equilibrium

Different kinds of networks, such as transportation, communication, computer, and supply networks, are susceptible to similar kinds of inefficiencies. These arise when congestion externalities make the cost for each user depend on the other users' choice of routes. If each user chooses the least expensive (e.g., the fastest) route from the users' common point of origin to the common destination, the result may be Pareto inefficient in that an alternative choice of routes would reduce the costs for all users. Braess's paradox represents an extreme kind of inefficiency, in which the equilibrium costs may be reduced by raising the cost curves. As this paper shows, this paradox occurs in an (undirected) two-terminal network if and only if it is not series-parallel. More generally, Pareto inefficient equilibria occur in a network if and only if one of three simple networks is embedded in it.     

Random-player games

This paper introduces general games with incomplete information in which the number, as well as the types or identities, of the participating players are determined by chance and might not be known to the players when they make their choices of actions. In these games, the selection of the number and types of players is modeled as a finite point process on a suitable type space. Definitions of pure-strategy, mixed-strategy, and correlated equilibria in random-player games are given, extending the corresponding ones for finite games, Bayesian games, and games with population uncertainty, which may all be considered as special cases of random-player games.     

Weighted congestion games with separable preferences

Players in a congestion game may differ from one another in their intrinsic preferences (e.g., the benefit they get from using a specific resource), their contribution to congestion, or both. In many cases of interest, intrinsic preferences and the negative effect of congestion are (additively or multiplicatively) separable. This paper considers the implications of separability for the existence of pure-strategy Nash equilibrium and the prospects of spontaneous convergence to equilibrium. It is shown that these properties may or may not be guaranteed, depending on the exact nature of player heterogeneity.     

Estimating Multiple-Discrete Choice Models: An Application to Computerization Returns

Buyers in many markets face multiple-discrete choices: they can purchase multiple-units as well as multiple-brands at the same time. This paper presents a multiple-discrete choice model for the analysis of differentiated products demand. Users maximize profits by choosing the number of units of each brand they purchase. I estimate the model using micro-level data on the demand for personal computers. I use the estimated demand structure to assess the welfare gains from computerization and technological innovation in peripherals. The estimated return on investment in personal computers is 92%. Moreover, a 10% increase in the performance-to-price ratio of microprocessors leads to a 2·2% gain in the estimated user surplus.