The bid-rigging on public works projects has recently become social problem in Japan. We can regard this issue as a framework of spatial game through simplifying the strategy of tendering. The main purpose of this study is to represent the tendering with multiple bidders as repeatedly playing games only with the opponents of relationships. We can regard cooperation to occur by performing the repeated games as bid-rigging. To examine the characteristics of this cooperation will lead to the discovery of new knowledge that prevents collusion.
From the point of view, in this research by the use of the agent based simulation, we have simulated the tendering recently conducted regarding the disposition of public properties and studied the characteristics of cooperation based on the decision with the suppression of desire. When every group mutually makes the moderate decision, we observe cooperation at high level in the spatial game with the extended strategy expression. On the other hand, it is revealed that the probabilistic change in the connectivity of each group greatly influences that cooperation. This perturbation, therefore, is effective for the deterrence of collusive tendering. In addition, altering multiple parameters, we also show further inspections regarding the obtained results.