我們依循表態性投票並認為意識型態較偏激的選民會因為投票而獲得更高的效用。然而，根據意識型態的影響，選民會會考慮到自己與候選人間意識型態的差距。在給定上述假設後，兩位候選人先行選定其意識型態後，選民才決定是否投票以及所投人選。當選民因為表態投票途徑所得之效用不若工具投票途徑來的重要時，兩位候選人的意識型態將會收斂到中點。反之，當選民因表態投票途徑所獲得之效用較重要時，則兩位候選人的意識型態將會分開而且意識型態較溫和的選民就不會投票。
實證方面，我們檢驗美國全國選舉研究從1972年到2008年之間10屆的總統大選資料，並且用nested logit來估計選民因為表態投票途徑以及工具投票途徑所得效用之相對應的係數，實證資料的結果支持我們對於越偏激的選民越可能會去投票的猜測。

We follow the approach of expressive voting and consider that voters with more extreme ideology can enjoy higher utility after voting. However, along with effect of ideology, voters also take the difference of his ideology and candidate’s into account. Given the above assumptions, two candidates choose their ideology before voters decide whether and for whom to vote. Two candidates’ ideology converges to the middle point if voters’ utility generated by expressive voting approach is less important than by instrumental voting approach. In the opposite, two candidates’ ideology diverge and the voters with mild ideology refuse to vote in point if voters’ utility generated by expressive voting approach is more important.
We examine the ANES data of ten U.S. presidential elections from 1972 to 2008. The nested logit model is used to estimate the corresponding coefficients of voters’ utility generated by expressive voting approach and instrumental voting approach. The data supports our conjecture that voters with more extreme ideology are more likely to cast their votes.

1. 緒論 1
1.1 研究動機與目的 1
1.2 文獻回顧 1
1.3 研究方法與架構 2
2 模型假設與主要結論 3
2.1 選民重視自身意識型態時後選人之策略選擇分析 3
2.2 選民重視自身與候選人間意識型態差距時後選人之策略選擇分析 13
3 實證資料分析、方法與結果 19
3.1 實證資料分析、方法 19
3.2 實證結果 22
4 結論與建議 23
附錄 24
參考文獻 25

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