Can Duverger's Law be extended to SNTV? The case of Taiwan's legislative Yuan elections

Abstract

Duverger's Law relating the single-member plurality system and the two-party system has recently been extended to the single nontransferable vote (SNTV), a system used in Japan prior to 1994 and in use in the Republic of China on Taiwan. The extended Law suggests that in districts in which there are M winners, there will be M+1 viable candidates. Our analysis of the four Legislative Yuan elections in Taiwan since 1986 offers support for this extension in districts with small magnitudes, but it also confirms that the larger the district magnitude, the more likely it is that the number of candidates will be greater than M+1. We explain this result on the basis of the lower reliability of information when the number of candidates is large and on the deceptive nature of small vote percentages. Evidently as a direct consequence of the larger numbers of candidates, the larger the district magnitude the more proportional the electoral results tend to be, albeit up to a point, due to differential degrees of organization among the political parties in Taiwan.