Implications of Distance over Redistricting Maps: Central and Outlier Maps

Fuente: arXiv
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Autores principales: Esmaeili, Seyed A., Chakrabarti, Darshan, Grape, Hayley, Brubach, Brian
Formato: Preprint
Publicado: 2022
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author Esmaeili, Seyed A.
Chakrabarti, Darshan
Grape, Hayley
Brubach, Brian
author_facet Esmaeili, Seyed A.
Chakrabarti, Darshan
Grape, Hayley
Brubach, Brian
contents In representative democracy, a redistricting map is chosen to partition an electorate into districts which each elects a representative. A valid redistricting map must satisfy a collection of constraints such as being compact, contiguous, and of almost-equal population. However, these constraints are loose enough to enable an enormous ensemble of valid redistricting maps. This enables a partisan legislature to gerrymander by choosing a map which unfairly favors it. In this paper, we introduce an interpretable and tractable distance measure over redistricting maps which does not use election results and study its implications over the ensemble of redistricting maps. Specifically, we define a central map which may be considered "most typical" and give a rigorous justification for it by showing that it mirrors the Kemeny ranking in a scenario where we have a committee voting over a collection of redistricting maps to be drawn. We include running time and sample complexity analysis for our algorithms, including some negative results which hold using any algorithm. We further study outlier detection based on this distance measure and show that our framework can detect some gerrymandered maps. More precisely, we show some maps that are widely considered to be gerrymandered that lie very far away from our central maps in comparison to a large ensemble of valid redistricting maps. Since our distance measure does not rely on election results, this gives a significant advantage in gerrymandering detection which is lacking in all previous methods.
format Preprint
id arxiv_https___arxiv_org_abs_2203_00872
institution arXiv
publishDate 2022
record_format arxiv
spellingShingle Implications of Distance over Redistricting Maps: Central and Outlier Maps
Esmaeili, Seyed A.
Chakrabarti, Darshan
Grape, Hayley
Brubach, Brian
Computer Science and Game Theory
Artificial Intelligence
Computers and Society
Data Structures and Algorithms
In representative democracy, a redistricting map is chosen to partition an electorate into districts which each elects a representative. A valid redistricting map must satisfy a collection of constraints such as being compact, contiguous, and of almost-equal population. However, these constraints are loose enough to enable an enormous ensemble of valid redistricting maps. This enables a partisan legislature to gerrymander by choosing a map which unfairly favors it. In this paper, we introduce an interpretable and tractable distance measure over redistricting maps which does not use election results and study its implications over the ensemble of redistricting maps. Specifically, we define a central map which may be considered "most typical" and give a rigorous justification for it by showing that it mirrors the Kemeny ranking in a scenario where we have a committee voting over a collection of redistricting maps to be drawn. We include running time and sample complexity analysis for our algorithms, including some negative results which hold using any algorithm. We further study outlier detection based on this distance measure and show that our framework can detect some gerrymandered maps. More precisely, we show some maps that are widely considered to be gerrymandered that lie very far away from our central maps in comparison to a large ensemble of valid redistricting maps. Since our distance measure does not rely on election results, this gives a significant advantage in gerrymandering detection which is lacking in all previous methods.
title Implications of Distance over Redistricting Maps: Central and Outlier Maps
topic Computer Science and Game Theory
Artificial Intelligence
Computers and Society
Data Structures and Algorithms
url https://arxiv.org/abs/2203.00872