The paper presents the problem of choosing the representatives in an assembly when the whole electoral region is subdivided into electoral districts. Because of the two dimensions, geographical (districts) and political (parties), the problem is called bi-apportionment. The main focus of the...

The first pillars of social security systems widely differ across European countries both in the contribution rate and intra-generational redistribution. What would be the impact of these differences if EU citizens had free access to all systems? This paper aims to highlight some basic features...

In coalitional games with side payments, the core predicts which coalitions form and how benefits are shared. The predictions however run into difficulties if the core is empty or if some coalitions benefit from not blocking truthfully. These difficulties are analyzed in games in which an a...

The paper investigates information sharing communities. The environment is characterized by the anonymity of the contributors and users, as on the Web. It is argued that a community may be worth forming because it facilitates the interpretation and understanding of the posted information. The...

In a world with a tremendous amount of choices, ranking systems are becoming increasingly important in helping individuals to find information relevant to them. As such, rankings play a crucial role of influencing the attention that is devoted to the various alternatives. This role generates a...

This paper analyzes in a two-country model the impact of students' mobility on the country-specific level of higher educational quality. Individuals decide whether and where to study based on their individual ability and the implemented quality of education. We show that the mobility of students...

This paper analyzes the efficient design of insurance schemes in the presence of aggregate shocks and moral hazard. The population is divided into groups, the labour force in different sectors for instance. In each group, individuals are ex ante identical but are subject to idiosyncratic shocks....

The paper analyzes how uncertainty on traders' participation affects a competitive security market in which there are some informed traders. We show that discontinuities, or "crashes", can arise at equilibrium, even when no investor posts a priori an increasing demand. Because of uncertain...

Ranking systems are becoming increasingly important in many areas, in the Web environment and academic life for instance. In a world with a tremendous amount of choices, rankings play the crucial role of influencing which objects are 'tasted' or selected. This selection generates a feedback when...

This paper presents results on the transitivity of the majority relation and the existence of a median representative ordering. Building on the notion of intermediate preferences indexed by a median graph, the analysis extends well-known results obtained when the underlying graph is a line. In...