混合式選制下的投票思維：台灣與日本國會選舉變革經驗的比較

Abstract

邇來以融合「單一選區多數決制」與「比例代表制」兩種選制精神的「混合式選制」(Mixed or Hybrid Systems)，深受各界的重視。相關的研究除針對混合選制的內涵進行概念性界定與歸類，另外亦聚焦於該選制與多元社會的發展關連、與選民策略性分裂投票行爲的連結、對既有選舉文化及政黨競爭策略的互動、甚或對政黨體系形塑的影響等。本文則是透過「日本選舉研究」(JES)與「台灣選舉與民主化調查」(TEDS)所彙整的個體層次民調資料，比較台日兩國分別從「單記非讓渡投票制」變革爲「單一選區兩票並立制」後，選民投票思維乃至政黨體系發展等的差異。\n研究結果顯示，兩國選民在初次實踐新選制時的投票決策，甚或縱跨選制變革前後的動態投票轉移趨向，確實存在不同程度的差別。從選民一致分裂投票行爲模式的橫斷面分析而言，新選制實行後主要政黨雖均獲兩票高度的一致支持，但台灣不僅國民及民進兩主要大黨獲得的一致支持率較日本爲高，並且對於兩黨體制的形塑目標是較日本來得明確。再就投票動態轉移的跨時序分析來說，本文也發現選制變革後確實有利於大黨選票的聚集，且新選制後台灣選票聚集於主要大黨的比例，比日本情況更爲明顯。總括本文的分析結果，除了印證台灣在改採新選制後，有效政黨數較日本狀況更趨近於兩黨競爭的格局，另外實踐新制對小黨生存空間造成的壓縮效果，在台灣是比日本來得更爲負面。

Mixed or Hybrid electoral system, a combination of single-member district with plurality (SMD) and proportional representation (PR), has drawn a lot of attention from all over the world in the past few years. Recent studies have focused on its characters and classifications, its impact on the diversified social development, the connection with strategic voting behavior, the interaction with the campaign strategy and party competition, and the formulation of new party system. Based on the survey conducted by Japanese Election Study (JES) and Taiwanese Election and Democratization Study (TEDS), we compare the dynamic voting behaviors between Japan and Taiwan, since both of them follow the same routine of electoral transformation from SNTV to Mixed system.\nThe results show there do have some difference, especially the ticket splitting of the two ballots and the voting stability during system transition, between two countries. From the cross sectional data analysis, we find KMT and DPP received more consistent support in two separate ballots, comparing with the major parties in Japan. As for the panel data results, the convergence to major parties is confirmed in both countries while the trend is more obvious in Taiwan once again. In short, we find the small parties in Taiwan have relative little room for competition, comparing with those in Japan, under new Mixed system. The formulation of two party system is quite noticeable in Taiwan.