The Price of Neutrality for the Ranked Pairs Method

The complexity of the winner determination problem has been studied for almost all common voting rules. A notable exception, possibly caused by some confusion regarding its exact definition, is method ranked pairs. original version method, due to Tideman, yields a social preference function that irresolute and neutral. variant introduced subsequently uses an exogenously given tie-breaking rule therefore fails neutrality. latter one most commonly in area computational choice, it easy see computationally tractable. We show contrast, computing set winners selected Tideman's pairs NP-complete, thus revealing trade-off between tractability In addition, several known results concerning hardness manipulation possible necessary are shown follow as corollaries from our findings.