Polling in a proportional representation system

Christos Mavridis,Ignacio Ortuño-Ortín

doi:10.1007/s00355-018-1117-5

Christos Mavridis, Ignacio Ortuño-Ortín

Open Access

https://doi.org/10.1007/s00355-018-1117-5

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Abstract

We study the effects of opinion polls on election results in proportional representation systems. Moderate voters have preferences over the vote shares received by the parties so that an agent’s optimal voting decision might depend on the other agents’ behavior. A voter’s information about other voters’ behavior can be improved through a series of opinion polls. We show that the mass of undecided voters decreases monotonically with the number of polls, but may not necessarily disappear. Voters who remain undecided have centrist ideologies. On average a series of polls brings the society closer to complete information even though specific polls may push the election result away from the complete information case.

Highlights

The effects that opinion polls have on the electorate have been studied extensively
We study the effects of opinion polls on election results in proportional representation systems
We show that the mass of undecided voters decreases monotonically with the number of polls, but may not necessarily disappear

Summary

Introduction

The conclusion of the literature is that the publication of polls influences how the electorate votes (Myerson and Weber 1993; Morton et al 2015) This influence is the reason why many countries have restrictions on how, when and if a poll should be published. For other distributions of voters’ preferences, after a number of polls the undecided mass of agents stops decreasing and additional polls cannot provide any further information. It is important to mention that this model provides three predictions: (1) the positive correlation between undecidedness and centrist ideologies, (2) the non-monotonicity of vote shares with respect to the number of opinion polls and (3) the decrease of the mass of undecided voters when more polls are published. Each of these three predictions can be generated by other models but we do not know of any model that predicts the three of them at the same time

Related literature

Model description

Complete information equilibrium

Conclusions

Findings

Compliance with ethical standards