在選舉時，世界真實的經濟狀態是具有不確定性的。因此，我們嘗試建立一個包括兩位主流候選人以及一位極端候選人的模型；其中主流候選人會依據接受到的真實經濟狀態訊號來提出當選後要執行的政策，而極端候選人不論真實經濟狀態的情況為何，永遠都提出財政擴張的政策。選民分為最適政策追求者以及肉桶政策者：最適政策追求者希望將選票投給提出與經濟狀態吻合的候選人，對於肉桶政策者來說，他們僅將選票投給提出財政擴張政策的候選人。除此之外，最適政策追求者對於其中一個主流候選人具有既成偏好。分析結果發現，當最適政策追求者為多數時，在不同類型選民偏好一致時，第三位候選人的加入降低了資訊傳遞效果；在不同類型選民偏好不一致時，第三位候選人的加入增加了資訊傳遞效果。若肉桶政策者為多數時，不論選民事前偏好是否一致，加入第三位候選人都能使得資訊傳遞效果增加。

The electoral model contains two mainstream candidates and a third extreme candidate. Because the state of the economy is uncertain, we would like to understand how effective the mainstream candidates is to transmit the information regarding the current state of economy with the presence of the third candidate. There are two types of voters. Optimal policy pursuers, who want a policy which is aligned to the state of economy to be implemented. Also, optimal policy pursuers have preconceived ideas about the mainstream candidates. Pork barrel pursuers, who are biased towards fiscal expansionary the policy that is always proposed by the third candidate regardless of the true state of economy. Two cases are considered: one in which the optimal policy pursuers are majority; another one in which pork barrel pursuers are majority. When optimal policy pursuers are majority, and both types of voters' priors are like-biased, adding the third candidate cannot improve the effectiveness of transmitting information. If voters' priors are opposing-biased, adding the third candidate can improve the effectiveness of transmitting information. When pork barrel pursuers are majority, adding the third candidate
can always improve the effectiveness of transmitting information.

論文審定書....i
摘要....ii
Abstract....iii
第一章 緒論....1
第二章 模型....4
第三章 投票....8
第四章 三位候選人的資訊傳遞....11
第五章 肉桶政策者為多數選民....13
第六章 兩位主流候選人的資訊傳遞....17
第七章 兩位主流候選人在肉桶選民為多數下的資訊傳遞....21
第八章 結論.... 24
文獻回顧....26
附錄....27

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