dampens cooperation, though only slightly. Surprisingly, externalities are immaterial. If we control for beliefs, they even … we add beliefs as a control variable, we only find that externalities enhance cooperation, even if gains from collusion … expected. -- Oligopoly ; Collusion ; experiment ; Uncertainty ; negative externalities ; prisoner's dilemma …

goods provision embedded in a social context and find that in the absence of explicit norms externalities have almost no … effect. With an endogenously formed provision norm positive as well as negative externalities dampen provision as compared to … no externalities. We explain the surprisingly low provision under positive externalities by the providers' increased risk …