AMU - AMSE
5-9 Boulevard Maurice Bourdet, CS 50498
13205 Marseille Cedex 1
We examine the impact of informal risk sharing on risk taking incentives when transfers are organized through a social network. A bilateral partial sharing rule satisfies that neighbors share equally a part of their revenue. In such a society, correlated technologies generate interdependent risk levels. We obtain three findings. First, there is a unique and interior Nash-equilibrium risk profile, and it is in general differentiated and related to the Bonacich measure of the risk sharing network. Second, more revenue sharing enhances risk taking on average, although some agents may lower their risk level. Last, we find that under investment might often be observed.
This article explores individual incentives to produce information on communication networks. In our setting, efforts are strategic complements along communication paths with convex decay. We analyze Nash equilibria on a set of networks which are unambiguous in terms of centrality. We first characterize both dominant and dominated equilibria. Second, we examine the issue of social coordination in order to reduce the social dilemma.
We study the formation of a directed communication network in which agents distribute a fixed amount of resource over links. Indirect benefits transit through the path maximizing the product of link strength. In this environment, the wheel architecture is shown to be both the unique efficient and the unique Nash architecture.
Firms raise cost-reducing alliances before competing with each other, but cannot fully appropriate the shared knowledge. When spillovers disseminate through the network of alliances, link formation enables firms to capture more spillovers, but by doing so they become intermediary in the spreading of spillovers to other firms. This leads to the emergence of asymmetric networks.
We study rival firms' incentives in quality-improving Research and Development (R&D) networks. The analysis stresses the role of free riding associated to collaboration and three major consequences emerge: R&D efforts decrease with the number of partners, networks of alliances are over-connected as compared to the social optimum and the profitmaximizing number of alliances is possibly non monotonic (decreasing then increasing) with respect to inverse measure of product differentiation.
We study the formation of a communication network under perfect foresight. We show the existence of a non-monotonic relationship between the cost of link formation and the total number of links created in stable networks. This result enhances a dilemma between stable and efficient networks. Copyright Springer 2006
In a vertically differentiated oligopoly, firms raise cost-reducing alliances before competing with each other. It is shown that heterogeneity in quality and in cost functions reduces individual incentives to form links. Furthermore, both differentiated Cournot and Bertrand competition qualitatively similar incitations to form alliances.
We explore collective behaviors in a deterministic mode of interacting agents. We relate unanimity of diversity to the structura conditions of the interaction network.
No abstract is available for this item.
eng] The role of social networks in innovation diffusion remains a strategic question. In former works, we have introduced a relational learning, based on hebbian rule, that leads to a critical state, in which few agents reach structural positions of opinion leaders. In this paper, we show that the self-organization of an influence network, through social learning, is not a monotonie process, from the point of view of structural characteristics as well as of its diffusion performances. The notion of intermediarity, which derives directly from the concept of network, appears necessary to decrypt this evolution. By introducing the role of "weak ties" in the diverse diffusion regimes it is then possible to bring a new understan-ding of the phenomenon.
[fre] Le rôle des réseaux sociaux dans la diffusion de l'innovation demeure une question stratégique. Dans des travaux antérieurs, nous avons introduit un apprentissage relationnel, de type hebbien, qui conduit à un état critique, dans lequel certains agents acquièrent des positions, purement structurelles, de leaders d'opinion. Dans cet article, nous montrons que l'auto-organisation d'un réseau d'influence, par l'effet d'un apprentissage social, ne constitue pas un phénomène monotone, aussi bien du point de vue des caractéristiques structurelles du réseau que de celui de ses performances en diffusion. Ceci nécessite, pour être analysé, de recourir à la notion d'intermédiarité qui est inhérente au concept de réseau. Une analyse relative au rôle des "liens faibles" dans les différents régimes de diffusion devrait alors permettre d'offrir un éclairage nouveau sur cette dynamique d'évolution.