now are: and similarly for payoffs in the stealing and giving treatments.

We expect the decision to join to increase with the return from joining and to decrease or increase with the subject’s desire to participate in redistributive actions — depending on the subject’s preferences. The value of pt is randomized across rounds to vary the return from joining. The sequence of treatments (burning, stealing and giving) and γt are also randomized across rounds. The distribution of pt and γt are given in Table 2. The order of treatments, pt, and γt are randomized across sessions so that order effects cancel out and can be ignored in the analysis.

A subject chooses whether or not to join the group on the basis of the information provided. The subject then chooses how much to destroy, appropriate, or transfer within the group. Subjects who do not join the group keep their initial endowment eit as in Part 2. Subjects who join the group can only affect the endowment of triplet members who have also joined the group — which implies that they observe which members of their triplet have joined a group in this round. However, as in Part 1, subjects are never told the burning, stealing, or giving choices of other participants. They are only told their final aggregate payoff at the end of the experiment. As the next sub-section details, this does not allow subjects to infer the choices of other participants. Furthermore, the triplet sets are reshuffl ed for each round so that, within Part 3, a participant never plays against the same subjects twice. This rules out strategic play.

# Implementation

Table 2 details the different values of pt, γbt, γst and γgt that were used in the experiment. These values were chosen so as to generate suffi cient behavioral variation, based on initial sessions run at Oxford University in Fall 2012.<sup>5</sup> The Table shows how the order of treatments are randomized across sessions to ensure that order effects cancel out in the analysis.<sup>6</sup> The values of pt, γbt, γst and γgt are also randomized across sessions and rounds. The set of parameter vectors used in the experiments and other randomization details are common to all three countries.

The value of p is set to ensure that joining a group is always Pareto-enhancing for all players: p > 1 in all cases, and is often large. Since the endowment of player i is multiplied by p whether others join or not, in the absence of redistribution it is always Pareto improving for a subject to join, irrespective of whether others join. Redistribution also has effi ciency implications, however. In the giving treatment giving is always effi ciency enhancing since the cost of giving is set to a fraction γg < 1 of the amount given. In contrast, redistribution through stealing, burning or

> 5 These sessions used essentially the same z-tree code but experimented with different parameter values. We observed a high prevalence of stealing even for large values of gamma/high cost of stealing, so we retained fairly large γst for the main sessions reported here. For burning, large values of γbt resulted in hardly any burning. Hence we retained reasonably low values of γbt to induce experimental variation. For the giving treatment, the initial Oxford sessions showed very low levels of giving, and hardly any giving at all for γgt values larger than 1, that is, when giving is ineffi cient. Hence we only retain low values of γgt for the main sessions. 6 Within a session the treatment order is the same for all subjects. This is necessary because triplets are reshuffl ed after each round, and hence it is the only way to ensure that all subjects play the same number of treatments.

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