Electoral Systems and Threshold Effects: Quantitative Evidence from the Japanese Experience in the 1990s

The conventional wisdom in political science is that legislators’ electioneering practices are closely linked to the electoral systems in which they compete.1 Since electoral concerns are argued to shape legislators’ representation and policy decisions, understanding how electoral incentives differ across electoral systems is useful for explaining cross-national differences representation and policy. Despite the large literature on electoral systems and legislators’ behaviors, there are surprisingly few empirical studies testing the influence of electoral systems on legislators’ electioneering activities. Some recent cases of electoral reforms find little difference between candidates’ electioneering behaviors before and after changes in the electoral system, raising questions about the impact of electoral institutions on candidate behavior (e.g. Crisp and Ingall (n.d.); Otake (1998); McKean and Scheiner (2000)). In this paper, I test the theory that multi-member districts (MMD) provide incentives for legislative candidates to favor narrow subconstituencies by reducing the voteshare threshold that candidates need to secure a legislative seat (Myerson (1993); Shugart (2000); Ames (2001, 1995); Cox (1990)). The basic argument underlying this threshold effect theory is that if a candidate appeals to broad cross sections of a multi-member district’s electorate, she will leave herself vulnerable to challengers who can concentrate their resources on the Carey and Shugart (1995); Shugart (2000); Sartori (1976); Taagepera and Shugart (1989); Ames (1995,