政策認同下的投票效用與選擇：空間投票理論在不同選舉制度間的比較

Abstract

為探索選民對各種政策認同的程度，以及政策對政黨偏好與投票選擇的影響，本文利用空間投票理論來解釋2001年台灣選舉的一些情況。有別於國内多數的實證研究，本文推論出條件式勝算對數分析(Conditional Logit)是所有不連續選擇模型中，較正確地分析空間投票理論的一項工具。此外，本文也針對不相關選項的獨立性假設(Independence of Irrelevant Alternatives,IIA)作一討論。雖然IIA假設對許多選擇理論與模型是相當嚴格的條件，但經由Hausman檢定，也佐証條件式勝算對數分析結果的適當性。\r\n研究的結果發現，不同的選舉選民投票時所受的政策影響就不一樣。基本上，政策議題在縣市長選舉時的影響，的確比在選立委時來得大。在縣市長競選時，政黨須對選民在統獨、經濟環保、及社會福利三種議題的位置與方向特別注意；而在立委選舉時，除統獨傾向的拿捏需注意外，無須考量太多政策可能的影響。此外，研究也發現贊成統一、支持經濟發展、要求多社會福利、或偏政治安定的選民較傾向支持泛藍陣營；而支持獨立、主張加強環保、少管社會福利、或是贊成政治改革的選民，則傾向支持泛綠軍。

This paper is to explore how the policy issues affected the voting behavior in the 2001 election based on the spatial theory of voting. It applies Conditional Logit methodology, which is more appropriate and correct than Multinomial Logit in analyzing the impact of policy on voting behavior. This paper also points out a restriction that many discrete choice models have overlooked - the property of Independence of Irrelevant Alternatives (IIA) and as a matter, introduces the Hausman Test to exam the coefficient stability.\r\nThe results show that the voting behavior is significantly different under different electoral systems. Essentially, the policy issues, including the unification-independence issue, economic policy, welfare policy, influence the voting decision more profoundly in county magistrate election, than in the legislative election. In addition, those who prefer unification with China, economic development, more social welfare, and political stability are pro KMT, PSP or NP. On the other hand, the voters who favor independent from China, environment protection, fewer social welfare, and political revolution, are pro DDP and TSU.