投票選項模糊下之檢定與分析：2010年高雄市長選舉的不確定性及投票效應

Abstract

本文以2010年高雄市長選舉為背景，探討選舉過程中候選人的模糊性及選民面對這種不確定性下的投票反應。由於相關實證研究忽視政策立場之外的模糊效果，並囿限於從候選人的角度來解釋，本文因此另闢途徑，透過一系列的統計檢定模式─包括孔多塞贏家(Condorcet winner)的計算、多項勝算對數模型的不相關選項獨立性檢定(IIA test)、Stereotype Logit的區別性檢定(Distinguishability test)等，據以廣泛地鑑別選民投票時的選項模糊性。其中尤為特殊的是運用較少受矚目的Stereotype Logit，並提出當選舉面臨越來越多模糊性的狀況下，該模型將是投票行為研究無法避免使用的統計工具。根據不同模型及檢定數據的分析結果，關於這場選舉的模糊性本文得出幾點結論：第一，這場選戰並未產生絕對的孔多塞輸家，顯示選民對陳菊、楊秋興與黃昭順三位候選人的偏好排列並非井然有序；其次，這幾位候選人對選民而言也非完全相互獨立，檢定結果顯示選民的投票結構會因為參選組合的不同而改變；第三，選民特別無法有效區隔楊秋興與黃昭順這兩位參選人，但陳菊與其他兩人之間則沒有這種模糊定位的問題，換言之當年楊秋興退黨參選主要是影響泛藍的選票。

This paper, based on the 2010 Kaohsiung mayoral election, explores candidate ambiguity during the campaign and the corresponding voting behavior under a veil of uncertainty. Current research limits the ambiguity to the candidate`s unclear policy standpoints and disregards the notion that the ambiguity may simply reside in the voters` own uncertainty. To relieve these constraints, several statistical examinations, including estimating the Condorcet winner, the IIA test under Multinomial Logit, and the Distinguishability test under Stereotype Logit, are proposed to observe how voters directly respond to ambiguity. Among those, Stereotype Logit is especially emphasized and is anticipated to be the most fitting choice model to estimate voting behavior under uncertainty. According to the estimation results, there is couple ambiguity observed in this mayoral election: First, despite the outcome of Chen Chu as the Condorcet winner, there is no defined Condorcet loser in this campaign. It indicates that voters` preferences are not completely organized and transitive. Second, candidates in this election are not mutually independent from the voter`s perspective. People are likely to respond differently if one of the candidates stops the campaign based on the test results. Third, it is especially difficult for voters to distinguish between Yang Chiu-hsing and Huang Chao-shun. Chen Chu, on the other hand, has no ambiguity concern with the other candidates. This paper substantiates that Yang Chiu-hsing, defected from the DPP, mainly to attract pan KMT ballots.