Voting after the change: A natural experiment on the effect of electoral reform on party system fragmentation

AuthorPedro Riera
Published date01 March 2020
Date01 March 2020
DOIhttp://doi.org/10.1177/0192512118822891
Subject MatterArticles
https://doi.org/10.1177/0192512118822891
International Political Science Review
2020, Vol. 41(2) 271 –286
© The Author(s) 2019
Article reuse guidelines:
sagepub.com/journals-permissions
DOI: 10.1177/0192512118822891
journals.sagepub.com/home/ips
Voting after the change:
A natural experiment on the
effect of electoral reform on
party system fragmentation
Pedro Riera
University Carlos III of Madrid, Spain
Abstract
This article analyses the causal effect of the 1993 electoral reform in New Zealand on party system
fragmentation using the ‘synthetic’ control method. Previous studies using cross-national evidence suggest
that electoral reforms change the number of parties. However, they do not take into account possible
endogeneity problems and usually focus on their short-term effects. Since the electoral system in use in this
country before the change was first past the post (FPTP), I can create a ‘synthetic’ control democracy that
had the same institutional framework but did not modify the rules of the game. The results indicate that the
electoral reform produced the expected effects on party system size at the electoral level, but that these
effects tended to disappear in the long run. In contrast, electoral system effects at the legislative level were
larger and stickier over time.
Keywords
Electoral reform, party system fragmentation, New Zealand, endogeneity, synthetic control method
Major electoral reforms are believed to have strong effects on party system fragmentation. The
field in general takes as an axiom that electoral system changes modify the number of parties by
affecting the translation of parties’ votes into seats and the strategic calculations of voters and
elites. However, empirical works on this matter that employ appropriate research designs are still
scarce. A key reason for the lack of causal evidence in this regard is that electoral reforms are not
assigned randomly. Important contextual characteristics influence the adoption of electoral reform,
which in turn affects the likelihood of party system change. This article investigates the hypotheti-
cal impact of electoral reform in first past the post (FPTP) systems by using the switch to propor-
tional representation (PR) in New Zealand during the 1990s as a case study and employing the
synthetic control method to address possible endogeneity problems.
Corresponding author:
Pedro Riera, Department of Social Sciences, University Carlos III of Madrid, c/Madrid 135, Getafe, 28903, Spain.
Email: priera@clio.uc3m.es
822891IPS0010.1177/0192512118822891International Political Science ReviewRiera
research-article2019
Article
272 International Political Science Review 41(2)
New Zealand constitutes a perfect case study, because FPTP is the most frequently employed
electoral system in the world. More specifically, the New Zealand episode is especially interesting
for three reasons. First of all, major electoral reforms like this one are fairly uncommon in estab-
lished democracies (Lijphart, 1994). Hence, if we want to know the potential effects of the actual
abandonment of FPTP at the national level for the party system, we need to focus on the New
Zealand reform. Secondly, the electoral system in this country, in contrast to other cases of elec-
toral reform, has not changed again after 1993. Consequently, institutional instability in New
Zealand after this year is unlikely to have had a substantial mitigating effect on the impact of the
original electoral reform. More importantly, the pre-reform New Zealand system was described by
comparative scholars as ‘a virtually perfect example of the Westminster model of democracy’
(Lijphart, 1984: 16). In the period of hegemonic two-party politics that began in 1938, the effective
number of electoral parties rarely reached three.1
Yet, this pattern started to change radically in the mid-1990s and early 2000s, with an effec-
tive numbers of electoral parties of at least 3.5. During this period, the number of parties that ran
in elections grew, and arguments by the leaders of the major parties about wasted votes did not
deliver a reduction in party system fragmentation. Not surprisingly, the change registered in
New Zealand politics has been attributed, at least partially, to the effect of electoral reform.
However, little research has been carried out to assess the causal impact of the electoral rules
change on the party system, because examining the effects of electoral reforms usually involves
two big difficulties.
On the one hand, a pure time-series analysis of the institutional change and the evolution of the
New Zealand party system would be contaminated by the inflation in the number of parties regis-
tered in other established democracies after the erosion of the traditional social cleavages described
by Lipset and Rokkan in 1967 (Franklin et al., 1992). On the other hand, when the new electoral
rules were adopted, New Zealand differed from other FPTP countries in characteristics that are
thought to be related to party system fragmentation. Therefore, a simple comparison of the evolu-
tion of the New Zealand party system and the party system of the rest of FPTP democracies would
reflect not only the effect of the electoral reform but also the effect of pre-reform differences in
determinants of the number of parties.
In order to tackle these problems, the synthetic control method is employed. According to
Abadie et al. (2015), this approach is useful to complement and facilitate comparative cases
studies in political science and allows us to know how the number of parties in New Zealand
would have evolved in the absence of electoral reform. More specifically, the analysis rests on
the following identification strategy: I use a combination of other FPTP countries to construct a
synthetic control majoritarian democracy that resembles relevant political characteristics of New
Zealand before the adoption of a PR system. The subsequent party system fragmentation of this
‘counterfactual’ New Zealand without reform is compared to the actual experience of New
Zealand. Doing so, it is possible to isolate the net effect of electoral system change, circumvent-
ing the problems of selection associated with the economic reforms of those years in New
Zealand and, above all, the process of enactment of the new electoral institutions. As in extant
empirical literature, observational data will be also used here, but I will adopt a sophisticated
research design to avoid endogeneity issues and validate or refute as a consequence previous
results. The research design adopted also allows studying the short- and long-term effects of
electoral reforms at the same time.
The article now proceeds to review previous works on the effects of electoral rules on party
systems. In the second section, I summarize the history of the New Zealand electoral reform. I then
elaborate on the research design adopted, presenting its important advantages, and overview the
main results. Finally, I draw some conclusions.

To continue reading

Request your trial

VLEX uses login cookies to provide you with a better browsing experience. If you click on 'Accept' or continue browsing this site we consider that you accept our cookie policy. ACCEPT