National teams from different continents can play against each other only in afew sports competitions. Therefore, a reasonable aim is maximising the number of intercontinental games in world cups, as done in basketball and football, in contrast to handball and volleyball. However, this objective requires additional draw constraints that imply the violation of equal treatment. In addition, the standard draw mechanism is non-uniformly distributed on the set of valid assignments, which may lead to further distortions. Our paper analyses this novel trade-off between attractiveness and fairness through the example of the 2025 World Men's Handball Championship. We introduce a measure of inequality, which enables considering 32 sets of reasonable geographical restrictions to determine the Pareto frontier. The proposed methodology can be used by policy-makers to select the optimal set of draw constraints.

A match played in a sports tournament can be called stakeless if at least one team is indifferent to its outcome because it already has qualified or has been eliminated. Such a game threatens fairness since teams may not exert full effort without incentives. This paper suggests a novel classification for stakeless matches according to their expected outcome: they are more costly if the indifferent team is more likely to win by playing honestly. Our approach is illustrated with the 2026 FIFA World Cup, the first edition of the competition with 48 teams. We propose a novel format based on imbalanced groups, which drastically reduces the probability of stakeless matches played by the strongest teams according to Monte Carlo simulations. The new design also increases the uncertainty of match outcomes and requires fewer matches. Governing bodies in sports are encouraged to consider our innovative idea in order to enhance the competitiveness of their tournaments.

This study investigates how present bias affects memory accuracy regarding earlier decisions in intertemporal decision-making. In a classroom experiment with university students, participants made choices between smaller, immediate rewards and larger, delayed rewards over two visits, followed by a third visit where they were asked to recall their prior decisions. Descriptive statistics reveal that participants with present bias exhibit lower memory accuracy compared to time-consistent peers, particularly in scenarios involving immediate rewards. Regression analysis confirms that motivated misremembering—recalling past decisions as more virtuous than they actually were—explains the reduced memory accuracy

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.