國立臺灣大學政治科學論叢

Abstract / Chinese PDF Download

In recent years, scholars have paid a great deal of attention to the influence of institutions on political behavior. The claim that “institutions matter” in politics is widely accepted. Empirical studies show that electoral systems have a great impact on parties, candidates, and voters with respect to nomination, coordination strategies, legislative behavior, voting behavior, electoral campaigns, and the development of party systems. Accordingly, when we try to understand the behavior and motivations of political actors, it is necessary to examine institutional rules.

After the electoral reforms of 1994, the single nontransferable vote (SNTV) was replaced with a mixed-member majoritarian (MMM) system. This paper seeks to evaluate the impact of this new electoral system based on district-level data. We are especially interested in the interaction effects (or the so-called “contamination effects”) on the two-vote structure resulting from dual candidacy strategies adopted by political parties. To avoid causal biased estimation and capture the contamination effect more precisely, we apply Heckman’s treatment-effects model to remove the endogeneity and self-selection problems. The result not only shows the dual candidacy strategies influence the interaction between two ballots, it also indicates the effect varies between different parties and different periods of time. More specifically, the dual candidacy strategy was especially beneficial to the Liberal Democratic Party’s (LDP) PR vote in 2009, the Democratic Party of Japan’s PR vote in 2003, and the Social Democratic Party’s (SDP) PR vote in 2000, 2005, and 2009. In conclusion, this study supports the existing literature on dual candidacy and contamination effects in mixed-member electoral systems.