立法院於2010年5月28日三讀通過將營利事業所得稅由25%調降至17%，並回溯自2010年度起實施，營利事業除了節省稅負之外，最重要的是強化台灣投資環境競爭力，外資更願意來台，有利未來營建、房地產業之發展。由於1986年至2009年營利事業所得稅最高稅率為25%已實施23年，過去探討營利事業所得稅對營建業股價影響之文獻並不多見，故本研究將以事件研究法來探討營利事業所得稅調降之事件是否會引起營建業股價之異常變動，實證結果發現不論使用OLS事件模型或GRACH事件模型，在營利事業所得稅調降宣告之後三日，營建業股價之平均異常報酬率及平均累積報酬率皆有正向且顯著的影響，證實了投資者對於營利事業所得稅調降之事件抱有樂觀正面的態度。 The Legislature Yuan passed the reduction of maximal corporation income tax rate from 25% to 17% on the evening of May 28, 2010 and implemented this law since 2010. The reduction of corporation income tax not only allows the construction companies to save tax burden, but most importantly strengthens the competitiveness of Taiwan's investment environment. Foreign investors are more willing to invest in Taiwan which benefits the future development of construction and real estate business. Generally speaking, it is an advantageous policy for construction industry. Though the maximal corporation income tax rate of 25% from 1986 to 2009 has been implemented for 23 years, previous researches seldom predicted that the corporation income tax would impact the stock price of the construction industry. This thesis applied the method of event study to investigate whether the legalization of reducing corporation income tax rate would cause irregular changes in stock price of listed construction companies, and to establish the regression model for analyzing the relationship between stock price changes and corporate financial structures. The empirical results of both OLS event model and GRACH event model show significantly positive cumulative average abnormal returns on three-day average abnormal returns and average cumulative return after the announcement of reducing corporation income tax. The data confirmed that the investors show optimistic positive attitude toward the issue of the reduction of corporation income tax.
