Almost optimal manipulation of a pair of alternatives
This work addresses manipulation risks in decision-making systems for stakeholders relying on expert rankings, though it appears incremental as it builds on existing pairwise comparison methods.
The paper tackles the problem of dishonest experts manipulating pairwise comparison rankings by proposing an algorithm to find an almost optimal way to swap two alternatives, enabling assessment of manipulation difficulty in specific cases.
The role of an expert in the decision-making process is crucial, as the final recommendation depends on his disposition, clarity of mind, experience, and knowledge of the problem. However, the recommendation also depends on their honesty. But what if the expert is dishonest? Then, the answer on how difficult it is to manipulate in a given case becomes essential. In the presented work, we consider manipulation of a ranking obtained by comparing alternatives in pairs. More specifically, we propose an algorithm for finding an almost optimal way to swap the positions of two selected alternatives. Thanks to this, it is possible to determine how difficult such manipulation is in a given case. Theoretical considerations are illustrated by a practical example.