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Activity Number: 335 - SRMS/SSS/GSS Student Paper Competition
Type: Topic Contributed
Date/Time: Tuesday, July 30, 2019 : 10:30 AM to 12:20 PM
Sponsor: Social Statistics Section
Abstract #301802 Presentation
Title: Polling Bias from Undecided Voters in Recent US Presidential Elections
Author(s): Joshua Bon* and Timothy Ballard and Bernard Baffour
Companies: Queensland University of Technology and University of Queesland and Australian National University
Keywords: Total survey error; Bayesian modelling; Election polling

Accounting for undecided and uncertain voters is a challenging issue for predicting election results. Undecided voters typify the uncertainty of swing voters in polls but are often ignored or allocated to each candidate in a simple deterministic manner. Historically this may have been adequate because undecided voters were sufficiently small to assume that they do not affect the relative proportions of the decided voters. However, in the presence of high numbers of undecided voters, these static rules may in fact bias election predictions from election poll researchers and metapoll analysts. We examine the effect of undecided voters in the 2016 US presidential election compared with the previous three presidential elections by extending a model proposed by Shirani-Mehr et al. (2018). We show that there were a relatively high number of undecided voters over the campaign and on election day, and that the allocation of undecided voters in this election was not consistent with two-party proportional (or even) allocations. We find evidence that static allocation regimes are inadequate for election prediction models and recommend probabilistic allocations be used in the future.

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