Putting a Compass on the Map of Elections

N. Boehmer, R. Bredereck, P. Faliszewski, R. Niedermeier, S. Szufa
IJCAI 2021
Abstract
In their AAMAS 2020 paper, Szufa et al. presented a "map of elections" that visualizes a set of 800 elections generated from various statistical cultures. While similar elections are grouped together on this map, there is no obvious interpretation of the elections' positions. We provide such an interpretation by introducing four canonical “extreme” elections, acting as a compass on the map. We use them to analyze both a dataset provided by Szufa et al. and a number of real-life elections. In effect, we find a new parameterization of the Mallows model, based on measuring the expected swap distance from the central preference order, and show that it is useful for capturing real-life scenarios.

Experiments:

Election type Culture Candidates Voters Instances Parameters
Ordinal PrefLib None None None https://www.preflib.org/dataset/00014
Ordinal PrefLib None None None https://www.preflib.org/dataset/00034
Ordinal PrefLib None None None https://www.preflib.org/dataset/00007
Ordinal PrefLib None None None https://www.preflib.org/dataset/00016
Ordinal PrefLib None None None https://www.preflib.org/dataset/00012
Ordinal PrefLib None None None https://www.preflib.org/dataset/00049
Ordinal PrefLib None None None https://www.preflib.org/dataset/00006
Ordinal PrefLib None None None https://www.preflib.org/dataset/00043
Ordinal PrefLib None None None https://www.preflib.org/dataset/00008
Ordinal PrefLib None None None https://www.preflib.org/dataset/00043
Ordinal PrefLib None None None https://www.preflib.org/dataset/00001
Ordinal Euclidean 1D {10} {100} None Uniform 1D {[0,1]}
Ordinal Euclidean 2D {10} {100} None Uniform 2D ($[0,1]^2$); Uniform 2D Sphere ($(0, 0)$ $r=1$)
Ordinal Euclidean 3D-or-more {10} {100} None Uniform 3D ($[0,1]^3$); Uniform 3D Sphere ($(0, 0)$ $r=1$); Uniform 5D ($[0,1]^5$); Uniform 5D Sphere ($(0, 0)$ $r=1$); Uniform 10D ($[0,1]^10$); Uniform 20D ($[0,1]^20$)
Ordinal Group-Separable {10} {100} None None
Ordinal Impartial Culture {10} {100} None None
Ordinal Mallows {10} {100} None None
Ordinal Single-Crossing {10} {100} None None
Ordinal Single-Peaked (Conitzer/Random Peak) {10} {100} None None
Ordinal Single-Peaked (Walsh/Uniform) {10} {100} None None
Ordinal Urn Model {10} {100} None None
Ordinal Mallows {20} {100} None None
Ordinal Urn Model {20} {100} None None
Ordinal Mallows {5, 10, 20, 50, 100} {100} None None