Collusive agreements are often observed in procurement auctions. They are probablymore easily achieved when competitors’ costs are easily estimated. If, however, the individualcosts of bidders are private information, effective ring formation is difficult to realize.We compare experimentally...

Social institutions regulating group conduct have been regarded as necessaryfor human cooperation to transcend family bonds. However, manystudies in economics and biology indicate that reciprocity based on repeatedinteraction suffices to establish cooperation with non-kin. We shedlight on the...