Specific Tastes or Cliques of Jurors? How to Reduce the Level of Manipulation in Group Decisions?

Abstract

We propose a modification of the standard Borda count which significantly reduces the level of manipulation demonstrated in experiments and observed in actual voting. The method may be applied in voting systems in which the Borda count is usually adopted, e.g. musical competitions, elections in educational institutions and professional and technical societies, sports awards, and even some political elections. We first analyze the actual voting results in the 2016 Henryk Wieniawski International Violin Competition. We show that some jurors are suspected of having exploited a weakness in the standard Borda count method to manipulate the final results. We then consider modifications of the Borda count with a view to designing a method more resistant to manipulation. We show that discarding all the scores of the 20% of jurors who deviate most from the jury average gives a ranking that agrees with public opinion and general expert consensus. Modifications of the Borda count were then experimentally tested against their resistance to manipulability. The results clearly show that excluding jurors has very good statistical properties to recover the objective order of the contestants. Most importantly, however, it dramatically reduces the level of manipulation demonstrated by subjects playing the role of jurors. Finally, we present the mathematical properties of the method proposed. We show that the new method is a compromise between the Majority Criterion and the standard Borda count in that it offers more “consensus-based” rankings than the former while being less vulnerable to manipulation than the latter.

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“…Thus, there is no universally effective method, but we can choose a method with special properties. Kontek and Sosnowska (2020) proposed an approach that may reduce the possibility of manipulation. This method was devised on the basis of the observation of the final of the 15th International Henryk Wieniawski Violin Competition.…”

Evaluated Post-Disaster and Emergency Assembly Areas Using Multi-Criteria Decision-Making Techniques: A Case Study of Turkey

“…The BORDA Counting method is a voting system that assigns points to each candidate based on their rank in each voter's preference list, with the winner being the candidate with the highest total score [57]. The BORDA Counting method is widely used in a variety of applications, including electoral systems, wine quality ranking, and waste management [57][58][59]. This method can also be used to reduce the amount of manipulation in group decisions [60].…”

Social Choice Rules, Fallback Bargaining, and Related Games in Common Resource Conflicts

“…The Borda scoring is often used in voting for the best state or to construct a ranking of the best states. It is also described as a consensusbased voting system because it can select a more broadly acceptable state over the one that has the support of not only a Plurality but even an absolute majority (Kontek and Sosnowska, 2020). While Borda scoring has been widely used, it has some potential flaws; it may violate the majority criterion, which states that, if a given state is the most preferred state for the players, that state should be the winner.…”