Discussion Papers 745
5 Experimental results
(17.78), the high-cost players’ effort (29.32), the low-cost players’ profit (113.38), its stan-
dard deviation (98.53), and the difference of the low-cost minus the high-cost players’ effort
are not significantly different from the respective value in the VOLUNTARY ASYM treatment.
Effort and profit of the low-cost players are not significantly different from those of the high-
cost players (Wilcoxon tests).
The low-cost players’ effort is significantly above their equilibrium effort and significantly
below their joint profit-maximizing effort (Wilcoxon tests, 5-percent significance). Recalling
that in voluntary teaming the low-cost players’ effort is not significantly different from their
joint profit-maximizing effort, we have thus got indirect evidence for higher effort by the
low-cost players in voluntary teaming compared to enforced teaming. The high-cost players’
effort is significantly above their equilibrium effort but not significantly different from their
joint profit-maximizing effort. This is similar to what we observe under voluntary teaming.10
Figures 2a and 2b show the density of team effort of the low- and the high-cost players, re-
spectively, under enforced and voluntary teaming. We see that under voluntary teaming the
observed effort levels are much less spread out than under enforced teaming.
The low-cost players’ profit is significantly different neither from their equilibrium profit nor
from their joint profit-maximizing payoff, while the high-cost players’ payoff is not signifi-
cantly different from their equilibrium payoff but significantly below their joint profit-
maximizing payoff (Wilcoxon test, 2-percent significance). In contrast to this, under volun-
tary teaming the high-cost players’ payoff is not significantly different from their joint profit-
maximizing payoff.
Conclusion 4: In the SYM treatment, we observe voluntary team effort that is higher than
enforced team effort. In the ASYM treatment, we observe less standard devia-
tion of the team effort choices by the high-cost players if teaming is voluntary
rather than enforced. It is only the high-cost players in the ASYM treatment
who gain a higher profit under voluntary teaming than under enforced team-
ing.
Prediction 5: Participants’ behavior is driven by reciprocity.
10 When we compare the first set of 15 periods to the last set of 15 periods, for neither player type, neither effort
nor profit shows a significant tendency to decrease or increase over time (Wilcoxon tests). The decrease in the
low-cost players’ effort, however, just fails significance. This is similar to voluntary teaming.
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