Laboratoire de Physique Théorique et Modélisatio, University de Cergy-Pontoise, France
The role of mutualistic interactions as market stabilizers
Unlike cooperative systems, where interacting agents put some effort together in order to achieve a common goal, in mutualistic systems, the agents’ goals may be very different and it is the interaction itself which is beneficial for the agents. The standard example of such systems is a plant-pollinator community, where the observed network of interactions shows a particular ordering called nestedness ; however, mutualistic interactions may be observed also in socio-economic systems. In this talk we explain how the tools developed to study ecosystems help to understand the role of social interactions in trading. In a vast economic literature concerning markets’ organisation, it is widely accepted that auction markets are the most efficient way of organizing the exchanges . However, it has recently been underlined that, when there exists no signal of quality for the goods, bilateral transactions allow people to gather information and better evaluate good’s intrinsic quality [3, 4]. We present a data based study of the Boulogne-Sur-Mer Fish Market, where the actors can daily choose to exchange either through a bilateral process or through an auction one. Since 2006, both sub-market forms operate at the same location, under the same conditions. Against what could have been expected, the more efficient structure taking over the other, both sub-markets coexist. Our results indicate that instead of competing, these sub-markets seem complementary. We show that their specificities can be directly measured from the corresponding interaction network, namely the development of trust relationships in the bilateral sub-market and the robustness of the auction one. This complementarity may be at the origin of the observed coexistence.
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