We study the effect of group size on cooperation in voluntary contribution mechanism games. As in previous experiments, we study four- and eight-person groups in high and low marginal per capita return (MPCR) conditions. We find a positive effect of group size in the low MPCR condition, as in previous experiments. However, in the high MPCR condition we observe a negative group size effect. We extend the design to investigate two- and three-person groups in the high MPCR condition, and find that cooperation is highest of all in two-person groups. The findings in the high MPCR condition are consistent with those from n-person prisoner’s dilemma and oligopoly experiments that suggest it is more difficult to sustain cooperation in larger groups. The findings from the low MPCR condition suggest that this effect can be overridden. In particular, when cooperation is low other factors, such as considerations of the social benefits of contributing (which increase with group size), may dominate any negative group size effect.

Abundant evidence suggests that high levels of contributions to public goods can be sustained through self-governed monitoring and sanctioning. This experimental study investigates the effectiveness of decentralized sanctioning institutions in alternative punishment networks. Our results show that the structure of punishment network significantly affects allocations to the public good. In addition, we observe that network configurations are more important than punishment capacities for the levels of public good provision, imposed sanctions and economic efficiency. Lastly, we show that targeted revenge is a major driver of anti-social punishment.

We investigate the endogenous formation of sanctioning institutions supposed to improve efficiency in the voluntary provision of public goods. Our paper parallels Markussen et al. (Rev Econ Stud 81:301–324, 2014) in that our experimental subjects vote over formal versus informal sanctions, but it goes beyond that paper by endogenizing the formal sanction scheme. We find that self-determined formal sanctions schemes are popular and efficient when they carry no up-front cost, but as in Markussen et al. informal sanctions are more popular and efficient than formal sanctions when adopting the latter entails such a cost. Practice improves the performance of sanction schemes: they become more targeted and deterrent with learning. Voters’ characteristics, including their tendency to engage in perverse informal sanctioning, help to predict individual voting.

Many social dilemmas exhibit nonlinearities and equilibrium outcomes in the interior of the choice space. This paper reports a laboratory experiment studying whether peer punishment promotes socially efficient behavior in such environments, which have been ignored in most experimental studies of peer punishment. It compares the effectiveness of peer punishment in a linear public good game to the effectiveness of this decentralized enforcement mechanism in two nonlinear social dilemma games: a piecewise linear public good game and a common pool resource game. While peer punishment improves cooperation in these new environments, the impact of punishment is weaker and takes longer to be effective. This appears to be due to the greater complexity of the nonlinear settings, which makes socially optimal choices more difficult to identify.

When every individual’s effort imposes negative externalities, self-interested behavior leads to socially excessive effort. To curb these excesses when effort cannot be monitored, competing output-sharing partnerships can form. With the right-sized groups, aggregate effort falls to the socially optimal level. We investigate this theory experimentally and find that while it makes correct qualitative predictions, there are systematic quantitative deviations, always in the direction of the socially optimal investment. Using data on subjects’ conjectures of each other’s behavior we investigate altruism, conformity and extremeness aversion as possible explanations. We show that deviations are consistent with both altruism and conformity (but not extremeness aversion).

Previous research demonstrates that individuals vary in their social preferences. Less well-understood is how group composition affects the behavior of different social preference types. Does one bad apple really spoil the bunch? This paper exogenously identifies experimental participants’ social preferences, then systematically assigns individuals to homogeneous or heterogeneous groups to examine the impact of ‘bad apples’ on cooperation and efficiency. Consistent with previous research, we find that groups with more selfish types achieve lower levels of efficiency. We identify two mechanisms for the effect. First, the selfish players contribute less. Second, selfish players induce lower contributions from the conditional cooperators, and this effect increases in the number of selfish players. These results are not sensitive to information about the distribution of types in the group.

Punishment has been shown to be an effective reinforcement mechanism. Intentional or not, punishment will likely generate spillover effects that extend beyond one’s immediate decision environment, and these spillovers are not as well understood. We seek to understand these secondary spillover effects in a controlled lab setting using a standard social dilemma: the voluntary contributions mechanism. We find that spillovers occur when others observe punishment outside their own social dilemma. However, the direction of the spillover effect depends crucially on personal punishment history and whether one is personally exempt from punishment or not.

When public goods can only be provided when donations cross a minimum threshold, this creates an advantage in that Pareto Efficient outcomes can be Nash Equilibria. Despite this, experiments have shown that groups struggle to coordinate on one of the many efficient equilibria. We apply a mechanism used successfully in continuous public goods games, the Hired Gun Mechanism (Andreoni and Gee in J. Public Econ. 96(11–12):1036–1046, 2012), to see if it can successfully get subjects across the threshold. When we use the mechanism to eliminate only inefficient equilibria, without addressing coordination, there is a modest but statistically insignificant improvement with the mechanism. However, when we hone the mechanism to eliminate all but one of the provision-point equilibria, thereby addressing the coordination issue, the mechanism moves all subjects to the desired efficient outcome almost immediately. In fact, after only one round using the hired gun mechanism, all subject are coordinating on the chosen equilibrium. The mechanism can be applied in settings where a group (1) has a plan for public good provision, (2) can measure contributions, (3) can fine members and (4) has an agreed upon standard for expected contributions. In these settings simple punishments, when focused on solving coordination as well as free riding, can greatly improve efficiency.