Mixed-member proportional electoral systems – the best of both worlds?

ABSTRACT

Mixed electoral systems are often associated with the hope of combining proportional election outcomes with a concentrated party system, and thus achieving the best of both worlds in electoral system design. It is especially the mixed-member proportional (MMP) variant that has retained a good reputation in this regard. Via a comparative analysis, we analyze whether or not the general praise for MMP systems is corroborated empirically. Our results show that the performance of MMP systems is heavily influenced by technical details, and elections conducted under MMP vary broadly with regard to possible proportionality–concentration combinations.

Acknowledgements

This manuscript has been written in the context of the research project “The Comparison of Electoral Systems’ Functions with a Special Focus on Mixed Systems”. We are grateful to the German Research Foundation (DFG) for support. A former version of this paper has been presented at the 24th IPSA World Congress in Poznań. We thank the participants of the panel “Electoral Systems and Representational Equality” for suggestions. Further, we thank Kay Grunenberg for his assistance. Finally, we are grateful to three anonymous reviewers for very valuable comments.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes on contributors

Eric Linhart is Professor for Political Systems at the Chemnitz University of Technology. His research interests include electoral systems, voting behavior and coalition theory. His publications have appeared, among others, in European Political Science Review, Party Politics, Public Choice and West European Politics.

Johannes Raabe is Research Associate at the Political Science Department at the University of Kiel. His research focuses on electoral systems and coalition governments. He has (co-)authored articles in European Political Science Review, Party Politics, West European Politics and International Political Science Review.

Patrick Statsch is a PhD candidate at the Department of Political Science at the University of Amsterdam. His research interests include interest groups, political parties and electoral systems.

Supplementary material

Lists of all cases which are included in our dataset are given in the Online Appendix which can be accessed at https://www.tu-chemnitz.de/phil/politik/pspi/forschung/daten/JEPOP_MMP_dataset.xlsx.

Notes

1 For positive evaluations of MMP systems, see also Bowler, Farrell, and Pettitt (2005), Gallagher (2005, 575), but see Bochsler (2012).

2 Our analysis does not include positive vote transfer systems as applied formerly in Italy or currently in Hungary and Romania. Those systems are similar to MMP systems (Bochsler 2014, 113) but usually categorized as a mixture of MMP and MMM systems (Benoit 2005, 235; Massicotte and Blais 1999, 357).

3 Notably, not all German Länder have always used MMP systems. In particular, the states of Bremen, Hamburg and the Saarland have never applied any form of MMP. The Online Appendix lists all cases which are included in our dataset. Missing Länder elections have not taken place under MMP.

4 For this reason, positive vote transfer systems, in which this is not the case, are not MMP systems in a narrower sense (cf. footnote 2).

5 Details can be found in the Online Appendix (cf. footnote 3; see also Massicotte 2003).

6 Raabe et al. (2014, 298) have shown that the number of votes does not impact the concentration of the party systems or the disproportionality of the elections in the German Länder. For this reason, we omit a discussion of this variable from here on.

7 Precisely, the number of list votes a party has gained within each PR district is divided by the number of SMDs already won by that party within this district and thus all seats – SMD and PR seats – are considered for the allocation of the PR seats. The quotient used for the allocation of every PR seat thus is calculated by dividing the list votes gained by party i through the number of seats already won by party i – plus one. For example, if party A gained 120,000 list votes and swept 4 district seats, the first divisor in the allocation of the PR seats for that party would be 5 (4+1), leading to a quotient of 24,000. If party B gained more than 24,000 list votes without having won a district seat, the first PR seat to be allocated would go to party B.

8 In New Zealand, the legal threshold is not applied to parties with at least one successful district winner. In Germany, the same rule exists, but since 1957, three district winners are necessary to bypass the legal threshold. Similar rules can be found on the Länder level.

9 Venezuela is a special case as not all representatives in the plurality tier are elected in SMDs. In 1997, for example, 71 of 102 plurality tier representatives are elected in SMDs, 18 in two-member districts, 9 in three-member districts and 4 in a four-member district. As the large majority of representatives in the plurality tier are still elected in SMDs, the other district magnitudes are very small, and plurality is still the applied election rule, this point seems negligible.

10 In Bolivia, the overall number of seats is constant. However, if a party wins more SMD seats in a region than it gets according to the PR mechanism, all district winners are elected anyway and the number of additional list seats available for PR allocation is reduced.

11 In such cases it might be questionable to base the calculation of the disproportionality on the PR tier vote distribution. Yet there are good reasons for doing so. First, this approach is in accordance with the general logic of MMP systems to provide proportional representation. Second, due to this coherence, using the PR vote distribution as a basis helps to detect cases where election outcomes deviate strangely from what we would normally expect from this type of electoral system.

12 Since the manipulation strategy in these three cases is based on their inherent compensation mechanism, MMP systems are generally vulnerable to this strategy. However, Lesotho’s reform of the electoral system in 2012 after which voters only have one fused vote for both tiers renders the manipulation strategy infeasible. The strategy would also be fruitless in those MMP systems with leveling seats. However, it is quite clear that variations in technical details such as district magnitude or legal threshold cannot prevent extreme outcomes – the electoral systems where strategic exploitation occurred vary considerably (see Table 1).

13 We thank one of the reviewers for this suggestion.

14 One reviewer recommended to run regression analyses in order to find out which of the discussed variables significantly influence the performance of MMP systems. While we generally like this idea, we decided not to show such results because of the presence of high levels of heteroscedacity in all respective models.

15 We use OECD membership of a country as a proxy variable.

Additional information

Funding

This work was supported by Deutsche Forschungsgemeinschaft [grant Number LI 1656/4-1].