Using different variants of the classic climate game, we investigate the role of competition and the source of endowment (windfall vs. earned). Participants completed a detailed personality test (including climate attitudes and economic preferences) before the experiment and were asked about their strategies afterwards. We find that competition did not significantly affect whether groups reached the target, even though the probability of achieving the common goal was lower in the presence of competition. Participants cooperated more when they had to earn the endowment. Based on the pre-experiment questionnaire, participants who viewed their personal actions as more important and effective in combating climate change were more likely to cooperate in the climate game, while the rest of the measured personality items did not exhibit a consistent pattern. Analysis of the post-experiment survey indicates that those who aimed to maximise earnings contributed less to the common pool. In contrast, those who believed the goal was achievable and aimed to achieve it contributed more to the common pool throughout the game.

We study three basic welfare axioms for school choice mechanisms with a reserve or quota-based affirmative action policy, namely non-wastefulness, respecting the affirmative action policy, and minimal responsiveness, and show that none of the previously proposed mechanisms satisfy all of them. Then we introduce a new mechanism which satisfies these three axioms. This mechanism issues immediate acceptances to minority students for minority reserve seats and otherwise it employs deferred acceptance. We analyze the fairness and incentive properties of this newly proposed affirmative action mechanism and provide possibility and impossibility results which highlight the trade-offs.

See at https://arxiv.org/abs/2310.08881

Multi-stage tournaments consisting of a round-robin group stage followed by a knockout phase are ubiquitous in sports. However, this format is incentive incompatible if at least two teams from a group advance to the knockout stage where the brackets are predetermined. A model is developed to quantify the risk of tanking in these contests. The suggested approach is applied to the 2022 FIFA World Cup to uncover how its design could have been improved by changing group labelling (a reform that has received no attention before) and the schedule of group matches. Scheduling is found to be a surprisingly weak intervention compared to previous results on the risk of collusion in a group. The probability of tanking, which is disturbingly high around 25%, cannot be reduced by more than 3 percentage points via these policies. Tournament organisers need to consider more fundamental changes against tanking.

We consider clustering in group decision making where the opinions are given by pairwise comparison matrices. In particular, the k-medoids model is suggested to classify the matrices as it has a linear programming problem formulation. Its objective function depends on the measure of dissimilarity between the matrices but not on the weights derived from them. With one cluster, our methodology provides an alternative to the conventional aggregation procedures. It can also be used to quantify the reliability of the aggregation. The proposed theoretical framework is applied to a large-scale experimental dataset, on which it is able to automatically detect some mistakes made by the decision-makers.

Qualifications for several world championships in sports are organised such that distinct sets of teams play in their own tournament for a predetermined number of slots. This paper provides a reasonable approach to allocate the slots based on historical matches between these sets of teams. We focus on the FIFA World Cup due to the existence of an official rating system and its recent expansion to 48 teams. Our proposal extends the methodology of the FIFA World Ranking to compare the strengths of five confederations. Various allocations are presented depending on the length of the sample, the set of teams considered, as well as the frequency of rating updates. The results show that more European and South American teams should play in the FIFA World Cup. The ranking of continents by the number of deserved slots is different from the ranking implied by FIFA policy. We recommend allocating at least some slots transparently, based on historical performances, similar to the access list of the UEFA Champions League.