本文主要目的有二：首先，在考慮非意欲產出（undesirable outputs）下， 比較假設廠商縮減因子皆相同以及允許有不同縮減因子時，兩種不同弱可拋設 定之生產邊界差異；其中，同時也比較傳統方向距離函數（directional distance function，以下簡稱DDF）與Russell 方向距離函數（Russell directional distance function，以下簡稱RDDF）的不同效率計算方法之差異。其次，衡量農會信用 部生產過程衍生的信用風險之影子價格（shadow price，以下簡稱SP），以了解 降低信用風險之機會成本。實證結果為：（1）不論DDF 或RDDF，在不同弱可 拋設定邊界下所得的結果，其差異都非常地小，因此對效率衡量結果的影響並 不明顯；（2）DDF 與RDDF 的結果，不論在何種邊界設定下，所得的無效率值 皆有顯著的差異，表示忽略非零差額之射線式衡量模式會造成無效率值的嚴重 低估；（3）根據RDDF 的結果，農會信用部約有59% 的改善空間，無效率的來 源為非意欲產出，表示農會信用部改善非意欲產出的效率，比改善意欲產出來 得重要；（4）非意欲產出的信用風險價格，大致呈現隨時間而逐漸增加的趨 勢，說明在2005 年前降低信用風險的機會成本較低，爾後在農業金融法的規範 下，確實能讓農會信用部的信用風險之機會成本變高，亦使得非意欲產出得逐 年降低，顯示金融法制規範的健全有利於信用部風險的控管。

The purpose of this study is to employ the technology frontiers with two different weak disposability specifications, to evaluate the operating performance and the opportunity cost of credit risk of the farmers’ credit unions (FCUs) in Taiwan over the period of 2001-2009 by using the DEA approach considering undesirable outputs. The evaluation includes twofold. Firstly, the weakly disposable technologies modeled with uniform and non-uniform abatement factors are both adopted to calculate the technical efficiency scores and the shadow prices of the bads of FCUs by both of the radial directional distance function (DDF) and non-radial Russell directional distance function (RDDF). The obtained results are compared to show whether the different specifications of the technology have significant impacts on the results. Secondly, statistic tests are adopted to examine the impacts of the implementation of the “Agricultural Finance Law”. The empirical results indicated: (1) The results of the comparisons of the Shephard and Kuosmanen technology frontiers indicate that they are very approximate for our data set, and thus the adoption of these two different technologies do not make significant difference on our results. (2) For the comparisons of the results of DDF and RDDF, it shows they are significant different from each other which implies the ignorance of the non-zero slacks would severely underestimate the evaluated inefficiency scores. (3) According to the results of RDDF, the average inefficiency value is about 0.59 and inefficiency is mainly from the poor performance of the reduction of bad outputs. Therefore, it suggests that it is more important for FCUs to decrease their production of bad loans to improve their performances. (4) For the opportunity cost of credit risk, it is found that it turns out to be increasing with the time. In addition, the cost is significantly larger for the period after the implementation of the “Agricultural Finance Law” and shows that the regulation implemented by the “Agricultural Finance Law do have positive effects on the control of the credit risk of FCUs.