Computing the Margin of Victory in Preferential Parliamentary Elections

TL;DR

This paper presents a method for automatically computing election margins in preferential parliamentary elections, enabling rigorous statistical audits and enhancing election integrity.

Contribution

It introduces a novel automated approach to determine vote changes needed to alter parliamentary outcomes, applicable to various electoral systems.

Findings

Applied to 2015 NSW Legislative Council election

Demonstrated feasibility for automated election auditing

Potential for broader use in electoral integrity measures

Abstract

We show how to use automated computation of election margins to assess the number of votes that would need to change in order to alter a parliamentary outcome for single-member preferential electorates. In the context of increasing automation of Australian electoral processes, and accusations of deliberate interference in elections in Europe and the USA, this work forms the basis of a rigorous statistical audit of the parliamentary election outcome. Our example is the New South Wales Legislative Council election of 2015, but the same process could be used for any similar parliament for which data was available, such as the Australian House of Representatives given the proposed automatic scanning of ballots.