選舉結果機率之分析：以2006年與2008年台灣選舉為例

Abstract

本文利用「未來事件交易所」的交易資料，分析預測市場「是否預測型」合約能否準確預測選舉結果，合約包括2006年的北高市長選舉、2008年的立委選舉及總統大選。本文分成四個部份分析「是否預測型」合約的準確度：加權平均價格與事件發生機率；加權平均價格與該合約結果的迴歸分析；五項比率（正確率、精準率、命中率、假警報率與貴氏比率差）分析；三項穩健性測試。本文發現：1、選舉當選預測合約的加權平均價格能充分反映候選人當選機率；2、加權平均價格是影響當選與否的主要因素；3、預測市場的預測準確度高於民調機構；4、預測市場的準確度隨時間接近選舉而逐步提升。

Using trading data of the Exchange of Future Events, this paper analyzes whether yes-or-no contracts of prediction markets can accurately predict the election results, including Taipei and Kaohsiung mayoral election in 2006, legislator election and presidential election in 2008. This paper analyzes the accuracy of the yes-or-no contracts in four parts: volume-weighted average price and the probability of event occurrence, logit model analysis on the volume-weighted average prices and the results of these contracts, analysis of five rates (correctness rate, precision rate, hit rate, false alarm rate, Kuipers score), and three robustness tests. This paper finds that: 1. volume-weighted average price can reflect the probability of candidates winning elections; 2. volume-weighted average price is the main factor to predict the events; 3. the prediction accuracy of prediction markets is higher that of polling institutions; 4. the accuracy of prediction markets increases as the election day approaches.