Title:      A Spatial Model of Electoral Platforms

Authors:    Martin Elff

Entrydate:  2008-07-01 06:08:50

Keywords:   Parties, party families, electoral platforms, party
manifestos, spatial models, unobserved data, latent trait
models, EM algorithm, Monte Carlo integration, Monte Carlo EM,
importance sampling, SIR algorithm,
ideological dimensions

Abstract:   The reconstruction of political positions of
parties, candidates and governments has made considerable
headway during the last decades, not the least due to the
efforts of the Manifesto Research Group the and Comparative
Manifestos Project, which compiled and published a data set on
the electoral platforms of political parties from most major
democracies for most of the post-war era. A central assumption
underlying the coding of electoral platforms into quantitative
data as done by the MRG/CMP is that parties take positions by
selective emphases of policy objectives, which put their
accomplishments in a most positive light (Budge 2001) or are
representative for their current polital/ideological positions.

Consequently, the MRG/CMP data consist of percentages of the
respective manifesto texts that refer to various policy
objectives.

As a consequence both of this underlying assumption and of the
structure of the CMP data, methods of classical multivariate
analysis are not well suited to these data, due to the
requirements to the data for an appropriate application of these
methods (van der Brug 2001; Elff 2002). The paper offers an
alternative method for reconstructing positions in political
spaces based on latent trait modelling, which both re�ects
the assumptions underlying the coding of the texts and the
peculiar structure of the data. Finally, the validity of the
proposed method is demonstrated with respect to the average
position of party families within reconstructed policy spaces.
It turns out that communist, socialist, and social democrat
parties differ clearly from �bourgeois� parties
with regards to their positions on an economic left/right
dimension, while British and Scandinavian conservative parties
can be distinguished from Christian
democratic parties by their respective positions on a
libertarian/authoritarian and a traditionalist/modernist
dimension. Similarly, the typical political positions of green
(or �New Politics�) parties can be distinguished
from the positions of other party families.

http://polmeth.wustl.edu/retrieve.php?id=764

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