Hypercubewise Preference Aggregation in Multi-Issue Domains

V. Conitzer, J. Lang, L. Xia
IJCAI 2011
Abstract
We consider a framework for preference aggregation on multiple binary issues, where agents' preferences are represented by (possibly cyclic) CP-nets. We focus on the majority aggregation of the individual CP-nets, which is the CP-net where the direction of each edge of the hypercube is decided according to the majority rule. First we focus on hypercube Condorcet winners (HCWs); in particular, we show that, assuming a uniform distribution for the CP-nets, the probability that there exists at least one HCW is at least 1-1/e, and the expected number of HCWs is 1. Our experimental results confirm these results. We also show experimental results under the Impartial Culture assumption. We then generalize a few tournament solutions to select winners from (weighted) majoritarian CP-nets, namely Copeland, maximin, and Kemeny. For each of these, we address some social choice theoretic and computational issues.

Remarks: Considers CP-nets

Experiments:

Election type Culture Candidates Voters Instances Parameters
Ordinal Impartial Culture {4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768} {?} 20000 None
Ordinal Impartial Culture {4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768} {501, 601, 701, 801, 901, 1001} 10000 None