Markets and networks: the influence of interpersonal links on trades' efficiency

How to define and measure trust is still an enigma in economics, philosophy and sociology. This three papers thesis compares two different mechanisms-negotiated (decentralised) and auction (centralized)-on the basis of trust. Through an empirical study, the level of trust is evaluated and its impact is analysed on the Boulogne-sur-Mer Fish market characterised by a stable coexistence of these two mechanisms. The three papers are preceded by a general introduction and a literature review. Paper one aims at comparing the nestedness and the robustness of both submarkets. Social network tools of ecologists are applied in order to provide an answer.Paper two models trust creation on both structures from the buyer side using on the outcomes of transactions. Bipartite and projected graphs reveal the difference between submarkets. This thesis shows that the negociated market is marked by a higher level of trust as agents interact and are not fully informed about the market situation unlike the auction one where information is centralized. We believe that trust is a way out of risk when there is lack of information.