參選人的競選花費是提供選民認識自己與政見最直接的媒介,長期以來國外文獻顯示選舉支出確實對選舉結果有著深遠的影響力,可惜國內學界受限於參選人資金資料的欠缺,相關研究一直付之闕如。本文利用政治獻金法通過後,監察院提供的第七屆立委參選人競選支出,分析以Jacobson(1978)爲首的傳統競選支出理論,在台灣選舉應用的情形。此外,由於競選支出與選舉情勢之間具相互連動關係,因此一般迴歸式不可避免會產生齊時偏誤的問題,本文沿用國外相關研究所採的兩階段最小平方法(Two-stage least squares, 2SLS 或TSLS)來分析相關數據。結果顯示,除政黨提名及現任者優勢等因素會影響參選者得票狀況外,競選經費的多寡更會直接衝擊選舉結果,而其實際對選舉結果的影響本文歸納出以下三點模式:第一,無論是現任者或是挑戰者,參選人本身的支出越多其得票率會越高;第二,同選區對手的支出越多,對其他參選者的選票越不利;第三,現任者支出轉換成選票的邊際效果,遠較挑戰者來得低。這幾項結果,特別是對現任者支出作用的觀察,可說完全呼應了Jacobson的支出理論。
Campaign expenditure has been the most direct and efficient resource for candidates, since it provides the medium for the voters to know the candidates and their policy platforms. The previous literature also shows that the election result is profoundly influenced by the campaign spending. Unfortunately, there have been few related empirical studies in Taiwan prior to the passage of the Political Contribution Act. In this paper, we collect and analyze the campaign spending for the 2008 legislative election from the Control Yuan. Because of reciprocal causality between spending and the election outcome, two-stage least squares (2SLS) is adopted to capture the unbiased relationship between them. The results show that, in addition to the party nomination and the incumbency advantage, the campaign spending influences the election result in three different ways. First, regardless of whether he/she is an incumbent or a challenger, as long as the candidate spends more money, he/she may receive more votes. Second, the spending by the opponents in the same district has a negative impact on others' votes. Third, the marginal return on the incumbent's spending is less than that on the challenger's. In general, the results confirm the traditional campaign expenditure theory based on Jacobson (1978)'s seminal work.