Théories des jeux

Gabrielle Demange, directrice d’études Réseaux bancaires L’objectif de ce séminaire était d’examiner les interactions entre les institutions financières afin de mieux comprendre le développement des crises financières et l’impact des mesures de régulation. Une telle compréhension est indispensable pour proposer des règles de fonctionnement adéquates et robustes. La montée en puissance de la titrisation a modifié la distribution et la gestion des risques de crédit et amplifié les liens entre l..

Collective attention and ranking methods

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 feedback when the ranking is based on citations, as is the case for PageRank used by Google. The attention bias due to published rankings affects new stated opinions (citations), which will, in turn, affect the next ranking. The purpose of this paper is to investigate this feedback by studying some simple but reasonable dynamics. We show that the long run behavior of the process much depends on the preferences, in particular on their diversity, and on the used ranking method. Two main families of methods are investigated, one based on the notion of 'handicaps', the other one on the notion of peers' rankings

On the influence of a ranking system

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 the ranking is based on citations, as is the case for the widely used invariant method. The selection affects new stated opinions (citations), which will, in turn, affect the next ranking. The purpose of this paper is to investigate this feedback in the context of journals by studying some simple but reasonable dynamics. Our main interest is in the long run behavior of the process and how it depends on the preferences, in particular on their diversity. We show that multiple long run behaviors may arise due to strong self-reinforcing mechanisms at work with the invariant method. These effects are not present in a simple search model in which individuals are influenced by the cites of the papers they first read