The Centre of Biostatistics in conjunction with the Department of
Mathematics and Statistics invite you to our third seminar in the spring
series. Further details of the series are available at
www.ul.ie/biostatistics
Friday, March 7th
2:00pm
A-2002
Exploring Voting Blocs Within the Irish Electorate:
A Mixture Modelling Approach
Brendan Murphy (UCD)
Irish elections use a voting system called proportional representation
by means of a single transferable vote (PR-STV). Under this system,
voters express their vote by ranking some (or all) of the candidates
in order of preference. Which candidates are elected is determined
through a series of counts where candidates are eliminated and surplus
votes are distributed.
The electorate in any election forms a heterogeneous population; that
is, voters with different political and ideological persuasions would
be expected to have different preferences for the candidates. The
purpose of this article is to establish the presence of voting blocs
in the
Irish electorate, to characterize these blocs, and to estimate their
size.
A mixture modeling approach is used to explore the heterogeneity of
the Irish electorate and to establish the existence of clearly defined
voting blocs. The voting blocs are characterized by their voting
preferences, which are described using a ranking data model. In
addition,
the care with which voters choose lower tier preferences is estimated
in the model.
The methodology is used to explore data from two Irish elections. Data
from eight opinion polls taken during the six weeks prior to the
1997 Irish presidential election are analyzed. These data reveal the
evolution of the structure of the electorate during the election
campaign.
In addition, data that record the votes from the Dublin West
constituency of the 2002 Irish general election are analyzed to reveal
distinct
voting blocs within the electorate; these blocs are characterized by
party politics, candidate profile, and political ideology.
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