本文利用寡占競爭模型研究在ECFA之下，開放大陸產品進口的相關經濟效果，主要的研究結論有三項。首先，命題一顯示，如果進口中國產品會造成台灣廠商的總收益下降，則我國的GDP一定會隨之下降。其次，命題二、三及四顯示，中國進口品對台灣產品的替代性愈強，則其損害台灣廠商之利益與台灣經濟的可能性就愈高。第三，在相同的產品替代程度下，開放中國產品進口後，能使GDP增加所需的門檻最高，能使廠商之產量與利潤增加的門檻次之，而能使福利水準增加的門檻則最低。換言之，存在著一種可能性，亦即台灣廠商可能會圖一己之利而將生產線外移至中國，但是結果卻將造成台灣GDP的減損。上述三項結論是從寡占競爭模型與數值模擬分析中所獲得的結果，事實上也驗證了許多反對ECFA的觀點，而此應可視為本文對於經濟理論與政策之可能貢獻。但是，必須特別強調的是，本文其實只是一個部分均衡分析，其研究結果並不代表兩岸經貿協議的總合效果必然有害於台灣經濟。因為一個完整與全面性的ECFA評估分析，仍須依靠總體經濟模型方能完成。

Taiwan has recently negotiated a free trade agreement with China. This paper provides some insights into the debates on the effects of ECFA. Using a model of duopoly competition, this paper derives some important predictions regarding the effects of ECFA on the output, profit, welfare and GDP of Taiwan. First, Proposition 1 shows that if the total revenues of the local firm decreased after the import of China’s products, Taiwan’s GDP will be decreased too. Second, Proposition 2, 3 and 4 demonstrate that the higher the substitution effect of the import goods and the local products, the more likely that it will decrease the profits of local firms and the GDP of Taiwan. Third, the condition to increase the GDP is higher than the condition to increase the profits, the outputs and the welfares. Therefore, it is possible that the local firms will move their factories to the mainland China to grab more profits and damage the Taiwan’s GDP in consequence. Last but not least, it should be noted that most of the conclusions of this paper is based on a partial equilibrium model, the more general analysis is necessary to evaluate the effect of ECFA after all, however, it is beyond the scope of this study.