Bayesian forecasting of electoral outcomes with new parties' competition

Fuente: arXiv
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Auteurs principaux: Montalvo, José García, Papaspiliopoulos, Omiros, Stumpf-Fétizon, Timothée
Format: Preprint
Publié: 2016
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author Montalvo, José García
Papaspiliopoulos, Omiros
Stumpf-Fétizon, Timothée
author_facet Montalvo, José García
Papaspiliopoulos, Omiros
Stumpf-Fétizon, Timothée
contents This paper proposed a methodology to forecast electoral outcomes using the result of the combination of a fundamental model and a model-based aggregation of polls. We propose a Bayesian hierarchical structure for the fundamental model that synthesises data at the provincial, regional and national level. We use a Bayesian strategy to combine the fundamental model with the information coming for recent polls. This model can naturally be updated every time new information, for instance a new poll, becomes available. This methodology is well suited to deal with increasingly frequent situations in which new political parties enter an electoral competition, although our approach is general enough to accommodate any other electoral situation. We illustrate the advantages of our method using the 2015 Spanish Congressional Election in which two new parties ended up receiving 30\% of the votes. We compare the predictive performance of our model versus alternative models. In general the predictions of our model outperform the alternative specifications, including hybrid models that combine fundamental and polls models. Our predictions are, in relative terms, particularly accurate in predicting the seats obtained by each political party.
format Preprint
id arxiv_https___arxiv_org_abs_1612_03073
institution arXiv
publishDate 2016
record_format arxiv
spellingShingle Bayesian forecasting of electoral outcomes with new parties' competition
Montalvo, José García
Papaspiliopoulos, Omiros
Stumpf-Fétizon, Timothée
Applications
This paper proposed a methodology to forecast electoral outcomes using the result of the combination of a fundamental model and a model-based aggregation of polls. We propose a Bayesian hierarchical structure for the fundamental model that synthesises data at the provincial, regional and national level. We use a Bayesian strategy to combine the fundamental model with the information coming for recent polls. This model can naturally be updated every time new information, for instance a new poll, becomes available. This methodology is well suited to deal with increasingly frequent situations in which new political parties enter an electoral competition, although our approach is general enough to accommodate any other electoral situation. We illustrate the advantages of our method using the 2015 Spanish Congressional Election in which two new parties ended up receiving 30\% of the votes. We compare the predictive performance of our model versus alternative models. In general the predictions of our model outperform the alternative specifications, including hybrid models that combine fundamental and polls models. Our predictions are, in relative terms, particularly accurate in predicting the seats obtained by each political party.
title Bayesian forecasting of electoral outcomes with new parties' competition
topic Applications
url https://arxiv.org/abs/1612.03073