Centripetal and centrifugal incentives in mixed-member proportional systems
| Published date | 01 July 2018 |
| Author | Anna-Sophie Kurella,Thomas Bräuninger,Franz Urban Pappi |
| DOI | 10.1177/0951629818774855 |
| Date | 01 July 2018 |
| Subject Matter | Articles |
Article
Centripetal and centrifugal
incentives in mixed-member
proportional systems
Journal of Theoretical Politics
2018, Vol. 30(3) 306–334
©The Author(s) 2018
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DOI:10.1177/0951629818774855
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Anna-Sophie Kurella
Universität Mannheim, MZES, Germany
Thomas Bräuninger
Universität Mannheim, Fakultät für Sozialwissenschaften, Germany
Franz Urban Pappi
Universität Mannheim, MZES, Germany
Abstract
How does competition for first (candidate) and second ballot (party-list) votes affect the strategic
positioning of parties in mixed-member proportional systems? We study this question in a simula-
tion study of multiparty competition in the two tiers. In the first step, we use data from elections
for the German Bundestag to estimate individual vote function for each tier based on ideology,
policy, and valence incentives. We then use these parameter estimates to calibrate a model in
which parties compete for either first- or second-tier votes. Results suggest that parties may face
a dilemma when adopting a positional strategy. When national parties and their candidates hold
significantly different valences, large valence advantages generate centripetal incentives whereas
smaller valences exert a centrifugal pull. Overall, centrifugal incentives dominate the German
mixed-member system.
Keywords
Mixed electoral systems; Nash equilibrium; party competition; spatial model
1. Introduction
Plurality elections in single-member constituencies (first past the post (FPTP)) and pro-
portional representation (PR) of party-list votes in parliaments have reportedly distinct
impacts on the link between representatives and those represented, voter behavior, party
Corresponding author:
Anna-Sophie Kurella, Universität Mannheim, MZES, Baden-Württemberg, Germany.
Email: anna.kurella@mzes.uni-mannheim.de
Kurella et al. 307
systems, and party strategies. Regarding the effects of electoral systems on party pol-
icy dispersion, it is argued that plurality systems force parties to appeal to the median
voter and this gives rise to centripetal incentives in party competition, while under PR,
parties may profit from offering extreme platforms and this is thought to lead to cen-
trifugal incentives (Cox, 1990; Duverger, 1951). In contrast to the vast literature on the
consequences of pure FPTP and PR on party competition, much less is known about
the consequences of their combination in a mixed-member electoral system (MMS). Are
centrifugal and centripetal incentives also present in the two tiers of a MMS and, if so,
does one dominate the other? Or do they balance each other out? In this paper, we seek to
contribute to this ongoing debate on the specific impact of a MMS on party competition.
An established body of formal literature on two-candidate competition under plural-
ity rule shows that candidates or parties often have centripetal position-taking incentives.
This applies to canonical, one-dimensional, or multidimensional models of party com-
petition with parties that are policy- or office-seeking and can precisely predict voter
behavior. In slightly different settings, however, when parties are policy-motivated and
cannot predict the behavior of voters, candidates may also have centrifugal incentives
(Calvert, 1985; Duggan, 2008; Wittman, 1977).
Candidate incentives to not locate at identical positions show up in more recent mod-
els that consider behavioral and nonpolicy motivations of voters—notably models that
consider such valence attributes of parties or candidates as personal integrity, trustwor-
thiness, or competence (Ansolabehere and Snyder, 2000; Groseclose, 2001; Serra, 2010).
The literature on multicandidate competition is more discordant. Merrill III and Adams
(2002) found centrifugal incentives based on a simple vote model, including partisan bias
and valence: in other work, they found centripetal incentivesfor low valence parties when
parties were policy-seeking (Adams and Ezrow, 2009). Schofield (2007) derived neces-
sary and sufficient conditions for platform convergence in multiparty settings; however,
under different conditions, divergent strategies could be in equilibrium (e.g. Schofield
and Sened, 2005; Schofield and Zakharov, 2010; Schofield et al., 2011). The prevalence
of centrifugal incentives in multiparty competition is also supported by a comprehensive
empirical analysis by Gallego and Schofield (2016), which provides evidence for cen-
trifugal tendencies in PR systems, whereas in majoritarian systems centripetal tendencies
are reportedly strong and parties locate near the mean.
Here, we consider a third type of system, MMS, and study the centrifugal and
centripetal incentives in issue competition that parties face when they choose a policy
platform—one electoral platform, which must prove itself in two separate tiers with dif-
ferent electoral formulas. While our analysis focuses on the German MMS, the question
is whether, or to what extent, ‘one size fits all’ reaches beyond this specific case.1We
argue that it is also relevant to more recently implemented MMS systems, as in Japan or
New Zealand, and other systems that are characterized by two ballots and strong parties
who devise national policy strategies. It is also related to the literature on platform choice
with heterogeneous plurality districts (Callander, 2005; Rodden, 2010).
To understand multiparty competition, it is necessary to jointly understand voting
behavior and electoral strategy. Our research strategy is first to estimate individual vote
functions with real data and, second, to use a calibrated model of party competition to
study the effect of PR and FPTP rules on party positioning. We argue that the effect
of electoral rules on party competition in the different tiers is conditional on: (1) how
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