本研究旨在建構一個，同時考量「不完全競爭市場」與「成本結搆差異」之實證模型， 探究不完全競爭市場下之本國銀行合併效益，依此提供確切且具價值性之參考依搪。本 研究首先在不完全競爭市場假設下，推導利潤極大化一階條件，並結合總成本函數與成 本份額方程式，組成一個包含五條方程式之聯立迴歸方程式體系，以供推估本國銀行之 成本函數。在考慮技術效率與成本結構差異性方面，本研究利用厚邊界法（ThickFmmier Approach ; TFA)進行分析，首先將樣本資料分成四個群組，再利用上述建構之聯立迴歸 方程式體系，分別推估各群組之成本函數，並模擬本國銀行合併之成本節省效益。

The purpose of this research is to explore the cost efficiencies of mergence of Taiwan's banking firms as Multiproduct Oligopolies. Under the assumption of profit maximization, this research derives the first-order conditions for each banking firm by choosing two output quantities. Those optimal conditions together wilh the cost function and share equations form the system of five regression equations that is applied to estimate the cost function of Taiwan's Banking Firms. In view of technical efficiency and different cost structures, this research uses the Thick Frontier Approach (TFA) to simulate the cost efficiencies of mergence. First, the all hanking firms arc classified into four groups, and then uses the system of five regression equations to estimate the cost function and cost efficiencies of mergence.