District magnitude, electoral coordination, and legislative fragmentation

ABSTRACT

Theories of party systems suggest that more restrictive rules should lead to fewer parties. According to this line of reasoning, parties and voters should strategically respond to reforms in electoral rules, such as changes in district magnitude. That is, a decrease in district magnitude should decrease the size of the party system, whereas an increase in magnitude should enlarge the party system. Using a series of difference-in-differences models based on data from Brazilian municipalities before and after an exogenous reform in magnitude, I study the effects of this electoral reform on both electoral coordination and legislative fragmentation. Contrary to the expectation, the number of lists did not change after a decrease in magnitude. However, parties formed more pre-electoral coalitions in municipalities that lost seats. Voters also coalesced around fewer lists. Lastly, as expected, the reform produced a decrease in legislative fragmentation. Both mechanical and psychological effects were responsible for this modification in fragmentation.

KEYWORDS:

• District magnitude
• psychological effect
• mechanical effect
• proportional representation
• Brazil

Acknowledgements

I thank Brian F. Crisp and Guillermo Rosas for their valuable comments and suggestions.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes

1 Cox (1997) generalized Duverger's argument by proposing the existence of an upper bound on the number of political alternatives in a system, the M+1 rule.

2 The other ranges established in the Constitution were: (i) between 33 and 41 seats in municipalities with population between 1 and 5 million; and, (ii) between 42 and 55 seats in municipalities with population larger than 5 million.

3 Mira Estrela had 11 seats in 2000 and lost 2 after the decision.

4 The lawsuit was started by the Public Prosecution Service (Ministério Público) of São Paulo (da Rosa 2006). The effects of the STF and TSE’s decisions and attempts to revert them were publicized in newspapers and television news shows. See, for example, the coverage of these events on Rede Globo, the major media group in Brazil, and Folha de São Paulo, one of the major newspapers in the country (Folha de São Paulo 2004; Jornal da Globo 2004)

5 As noted in the previous section, there are two types of entrants in these elections: parties and pre-electoral coalitions. All dependent variables, in the main analysis, are calculated at the level of the entrant (parties or PECs). I present an analysis at the level of the party in Appendix F. The results in this appendix indicate that legislative fragmentation decreased, but more parties entered the elections. As shown below, this result is explained by the fact that parties formed more pre-electoral coalitions in the post-reform period.

6 Effective number of (legislative) parties is given by $1\mathrm{\setminus }{\sum }_{i=1}^n{p}_i^2$, where p is the proportion of votes (seats) received by the party i in the municipality (Laakso and Taagepera 1979).

7 Because the difference-in-differences design assumes that the composition of treated and control groups is stable over time, I restrict the analysis to municipalities that were created before the 1996 election and existed at least up to 2008. Moreover, I also remove municipalities that had their magnitude changed between the 2004 and 2008 elections because of population changes. The analyzed sample include 1,992 out of the 2,425 municipalities affected and 2,833 out of the 3,133 municipalities not affected by the 2004 reform. See Appendix B for the distribution of changes in magnitude in the final sample.

8 Although the creation of population thresholds by the 2004 reform makes the regression discontinuity design (RD) a possible choice, the sudden change in magnitude provoked by the TSE's decision precludes the use of such a design. The RD assumes that observations close to the cutoff point should be similar in terms of observed and unobserved characteristics (Angrist and Pischke 2009). The abrupt change in magnitude is an obvious confounder. In Appendix C, I show that municipalities above the threshold lost, on average, 1.1 fewer seats than those municipalities below the threshold. This indicates that the increase in magnitude at the cut-point is confounded by the change in magnitude produced by the 2004 reform, making the RD unsuitable for the analysis. One alternative would be to use the population required to lose a given number of seats as the running variable. However, there are few observations on the right-hand side of the cutoff (municipalities that could have lost seats). It occurs because most of the municipalities that did not lose seats already had the minimum number of seats allowed (see Table B.1). As a result, these municipalities could not lose any additional seats. Excluding these observations, there are only 23 municipalities that were not affected by the 2004 reform. Moreover, most of the municipalities (1,873 out of 2,415) lost the number of seats necessary to make their magnitude equal to nine seats, the minimum number of seats allowed by the constitution. Therefore, the majority of the municipalities could not lose more seats.

9 I present analysis for different treatment groups and elections in Appendix E.2.

10 Remember that the dependent variables are measured at the list level (PECs or parties running solo)

11 Ideally, I would consider only municipalities that did not change their magnitude since the first election after the promulgation of the 1988 Constitution. Unfortunately, data for elections before 1996 are not available.

12 Appendix D contains an example for the construction of the counterfactual scenarios.

13 I report estimates for subgroups in Appendix E.2.7. These reveal that the psychological effect was the main force behind the changes in most of the treated municipalities.

14 Note that the lack of statistical significance for some of components of the psychological effect does not mean that voters and elites behave in exactly the same manner before and after the reform. However, it means that changes in behavior were not enough to produce meaningful impacts on legislative fragmentation.