Mohamed Belhaj

  • Chercheur
Contact :

Aix-Marseille Université
5-9 Boulevard Bourdet, CS 50498
13205 Marseille Cedex 1
Téléphone : +33 (0)4 13 55 25 25
Ecole Centrale de Marseille
En détachement
Domaines de recherche :
Théorie des jeux et réseaux sociaux
Thèse :
University of Toulouse 1
Efficient networks in games with local complementarities, Mohamed Belhaj, Sebastian Bervoets et Frédéric Deroian, Theoretical Economics, Volume 11, Issue 1, pp. 357–380, 2016

We address the problem of a planner looking for the efficient network when agents play a network game with local complementarities and links are costly. We show that for general network cost functions, efficient networks belong to the class of Nested-Split Graphs. Next, we refine our results and find that, depending on the specification of the network cost function, complete networks, core-periphery networks, dominant group architectures, quasi-star and quasi-complete networks can be efficient.

Competing Activities in Social Networks, Mohamed Belhaj et Frédéric Deroian, The B.E. Journal of Economic Analysis & Policy, Volume 14, Issue 4, pp. 36, 2014

We consider a society in which each agent has one unit of a resource to allocate between two activities. Agents are organized in a social network, and each activity generates complementarities between neighbors. We find multiplicity of equilibrium for high intensity of interaction, and we characterize equilibria in terms of specialization and polarization. Overall, results reveal the crucial role played by network geometry. The results also suggest that the structure of the social network should be taken into account for the design of a public policy in favor of a specific activity.

Risk-Taking and Risk-Sharing Incentives under Moral Hazard, Mohamed Belhaj, Renaud Bourlès et Frédéric Deroian, American Economic Journal: Microeconomics, Volume 6, Issue 1, pp. 58-90, 2014

This paper explores the effect of moral hazard on both risk-taking and informal risk-sharing incentives. Two agents invest in their own project, each choosing a level of risk and effort, and share risk through transfers. This can correspond to farmers in developing countries, who share risk and decide individually upon the adoption of a risky technology. The paper mainly shows that the impact of moral hazard on risk crucially depends on the observability of investment risk, whereas the impact on transfers is much more utility dependent.

Network games under strategic complementarities, Mohamed Belhaj, Yann Bramoullé et Frédéric Deroian, Games and Economic Behavior, Volume 88, Issue C, pp. 310-319, 2014

We study network games under strategic complementarities. Agents are embedded in a fixed network. They choose a positive, continuous action and interact with their network neighbors. Interactions are positive and actions are bounded from above. We first derive new sufficient conditions for uniqueness, covering all concave as well as some non-concave best responses. We then study the relationship between position and action and identify situations where a more central agent always plays a higher action in equilibrium. We finally analyze comparative statics. We show that a shock may not propagate throughout the entire network and uncover a general pattern of decreasing interdependence.

Strategic interaction and aggregate incentives, Mohamed Belhaj et Frédéric Deroian, Journal of Mathematical Economics, Volume 49, Issue 3, pp. 183-188, 2013

We consider a model of interdependent efforts, with linear interaction and lower bound on effort. Our setting encompasses asymmetric interaction and heterogeneous agents’ characteristics. We examine the impact of a rise of cross-effects on aggregate efforts. We show that the sign of the comparative static effects is related to a condition of balancedness of the interaction. Moreover, we point out that asymmetry and heterogeneous characteristics are sources of non-monotonic variation of aggregate efforts.