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Home Issues Backissues Volume 31, No.1 An Empirical Analysis of the M+1 Rule and the Number of Effective Candidates: The Case of the Legislative Yuan Elections in Taiwan from 1989 to 2004

An Empirical Analysis of the M+1 Rule and the Number of Effective Candidates: The Case of the Legislative Yuan Elections in Taiwan from 1989 to 2004

Kuan-Cheng Lee and Tsung-Wei Liu
2008 / 05
Volume 15, No.1

pp.73-107
10.6612/tjes.2008.15.01.73-107
Paper

Abstract

According to ”the M+1 rule” proposed by Gary Cox, under the SNTV system the number of effective candidates tends to be limited into M+1 (M stands for district magnitudes). In fact, empirical studies show that the votes are not necessarily concentrated on M+1 candidates, since assumptions of the M+1 rule may be not always true in the real world. Parties can nominate candidates rationally and distribute the votes equally under certain circumstances, but they sometimes can not overcome the problems of coordination. Voters tend to vote strategically as long as they have perfect information. But the information is by no means costless in the real world. Therefore, when the deviations between the theoretical expectations and the empirical observations occur, it does not necessarily mean that the theory or model is false. The theory still stands true if the deviations can be explained systematically. The dependent variable of the study is the difference between the numbers of effective candidates and the numbers predicted by ”the M+1 rule.” Using the aggregate data of 167 districts of the Legislative Yuan Elections in Taiwan from 1989 to 2004, this paper finds that the district magnitude, party nomination strategies, successful vote distributions within parties' candidates, the quality of voters’ information and the learning effects are systematically correlated with the extent to which the effective numbers of candidates deviate from the M+1 rule. Overall, although the numbers of effective candidates are equal to M+1 in only a quarter of districts, the M+1 rule is supported by the empirical evidence of Taiwan.

Keywords

the M+1 rule

the effective number of candidates

district magnitude

problems of coordination

election context

trial and error