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SOE: Fachverband Physik sozio-ökonomischer Systeme

SOE 6: Poster Session

SOE 6.11: Poster

Montag, 31. März 2014, 18:00–20:00, P2

Spatial constraints and auspicious buying in a self-organized cartel formation model — •Philipp C. Böttcher, Tiago P. Peixoto, and Stefan Bornholdt — Institut für Theoretische Physik, Universität Bremen, Hochschulring 18, D-28359 Bremen, Germany

The decision of the German cartel office to require gas stations to record and release their gas prices to the public sparked considerable interest in the media. We investigated a simple trust game to qualitatively predict the effects of this decision.

In our model, a population of agents is forced to play against each other: Buyers buy from a fixed number of sellers that are chosen dynamically, and sellers can compare their payoff and adapt accordingly. The results for simulations on a globally mixed population [1] showed the existence of a phase transition, observed at a specific value for the strategy update rate, where the spontaneous formation of an effective cartel occurs. This suggested that a cartel can be formed without collusion and may simply be the result of individual payoff maximization. However, the model lacked important ingredients, such as the fact that both buyers and sellers are often constrained to specific geographical locations. To model this effect, we investigated the dynamics of the model on a 2D-lattice and introduced a distance of interaction. Finally, to model the effect of the global knowledge introduced by a general price list, we added a fraction of buyers who were fully aware of their neighborhood and were therefore able choose the best seller to buy from, instead of comparing with randomly chosen neighbors.

[1] T. Peixoto and S. Bornholdt, Phys. Rev. Lett. 108, 218702 (2012)