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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 of this question in a very simple two countries model. ; Les régimes de retraite de base des divers pays européens diffèrent par le niveau de leur taux de cotisation et par la redistribution effectuée au sein d'une même génération de retraités. Quel serait l'impact de ces différences si les citoyens de l'Union Européenne pouvaient choisir librement entre les divers régimes ? Nous tentons ici d'apporter quelques éléments de réponse à cette question en analysant un modèle très simple à deux pays.

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 of this question in a very simple two countries model. ; Les régimes de retraite de base des divers pays européens diffèrent par le niveau de leur taux de cotisation et par la redistribution effectuée au sein d'une même génération de retraités. Quel serait l'impact de ces différences si les citoyens de l'Union Européenne pouvaient choisir librement entre les divers régimes ? Nous tentons ici d'apporter quelques éléments de réponse à cette question en analysant un modèle très simple à deux pays.

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 of this question in a very simple two countries model. ; Les régimes de retraite de base des divers pays européens diffèrent par le niveau de leur taux de cotisation et par la redistribution effectuée au sein d'une même génération de retraités. Quel serait l'impact de ces différences si les citoyens de l'Union Européenne pouvaient choisir librement entre les divers régimes ? Nous tentons ici d'apporter quelques éléments de réponse à cette question en analysant un modèle très simple à deux pays.

A hierarchical structure is a widespread organizational form in many areas. My aim in this paper is to provide a rationale for this fact based on two premises. First, a group organizes itself so as to achieve efficient coordination. Second, efficient coordination is achieved only if subgroups as well as individuals agree to cooperate. Even in situations in which there are gains to coordination, the agreement of each possible subgroup may be impossible to reach, resulting in instabilities. I argue that a hierarchical organization avoids such instabilities by distributing in an optimal way autonomy and blocking power to a restricted set of subgroups. Comparisons with nondirected networks are drawn.

This paper defines and studies optimality in a dynamic stochastic economy with finitely lived agents, and investigates the optimality properties of an equilibrium with or without sequentially complete markets. Various Pareto optimality concepts are considered, including interim and ex ante optimality. We show that, at an equilibrium with a productive asset (land) and sequentially complete markets, the intervention of a government may be justified, but only to improve risk sharing between generations. If markets are incomplete, constrained interim optimality is investigated in two-period lived OLG economies. We extend the optimality properties of an equilibrium with land and examine conditions under which introducing a pay-as-you-go system would not lead to any Pareto improvement upon an equilibrium.

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. Often the allocation of seats to districts is pre-determined and furthermore distorted ---meaning that the ratios of the number of assigned seats to population size vary significantly across districts. The paper surveys proposed bi-apportionment methods with a focus on the conflict that may arise between party-proportional representation under district distortions.

Ranking systems are becoming a fundamental tool in many areas, including the Web environment for ranking pages. PageRank, the most popular method, is based on the links stemming from a page and defined so as to be immune to their inflation, a property called intensity-invariance. This paper introduces and characterizes a new intensity-invariant method, called the handicap-based method. The method assigns not only a ranking to the items but also weights to the experts on which the ranking is based. Ranking and weights form an equilibrium for a relationship based on the notion of handicaps. The method is, in a sense made precise in the paper, the counterpart of the counting method in environments that require intensity-invariance.

This paper proposes to measure the spill-over effects that cross-liabilities generate on the magnitude of default in a system of financially linked institutions. Based on a simple model and an explicit criterion -the aggregate debt repayments- the measure is defined for each institution, affected by its characteristics and links to others. These measures -one for each institutionsummarize relevant information on the interaction between the liabilities structure and the shocks to resources and they can be useful to determine optimal intervention policies. The approach is illustrated to evaluate the consolidated foreign claims of 10 EU countries

New regulations promote the role of Central Counter-Parties as insurers of counterparty risk to stabilize derivative markets. Most CCPs are for-profit institutions, competing for profits and market shares. Whether competition is harmful or beneficial to efficiency and financial stability is debatable, leading to different positions in the US and the EU. Assessing the impact of competition between CCPs is complex because of the many dimensions involved in their policies and the heterogeneity of their potential users, ranging from main intermediaries (the dealers) to final clients. We first review the business model of CCPs and illustrate the dimensions on which CCPs compete by gathering EU data on CCPs, their scopes, their clients and members. We then focus on the clearing of CDS by providing an empirical analysis of on the choices of CCPs by the main dealers.