利用開放體系下的寡佔理論模型的建立與推導，依據民國78-85年台灣中游石化業資料，以完全訊息最大概似法對對內銷PCM、進口比與內銷市場集中度三條聯立方程式進行估計。本文發現產能利用率對內銷PCM的影響是正面的，進口比對內銷PCM的影響是負的，並且都具有統計顯著性；內銷PCM、關稅與成本差異對進口比的影響是負的，且具有統計顯著性，內銷市場產業集中度對進口比的影響是正的，亦具有統計顯著性；內銷PCM與運輸成本對內銷市場產業集中度的影響是正的，且具有統計顯著性，而內銷市場規模對內銷市場產業集中度其有顯著負面效果。匯率並非影響中游石化業獲利率的重要因素；最後，內銷PCM、進口比與產業集中度皆存在顯著直接聯立關係。

在市場競爭不斷加劇之環境下，會計師事務所究竟要如何因應？削價競爭固然為一種經營策略，但並非長久之計。過去文獻指出，會計師事務所可藉由發展產業專業化以因應市場競爭，且會計師產業專精對審計公費有正向之影響。然而，過去文獻亦指出客戶產業特性對審計公費訂價有一定之影響力，故本研究目的乃在探討會計師產業專精對審計公費影響力之大小，及是否會計師產業專精對審計公費之影響力會大於客戶產業特性對審計公費之效果。實證結果顯示會計師產業專精與客戶產業特性兩者對審計公費皆有相當之影響力，但客戶產業特性對審計公費訂價之影響較大。另外，在將樣本區分為高科技產業與傳統產業後可發現，會計師在高科技產業之專長對客戶而言較具有價值，產業專精會計師在高科技產業對審計公費訂價之影響力較大、能夠收取較高之審計公費。 / How can accounting firms build up competitive advantages when they face increased competition? One way is to cut costs and decrease prices, but this may not be the best strategy in the long run. Casterella et al.(2004) suggest that product differentiation based on industry expertise may be a more sustainable solution because auditor specialization shows a significantly positive association with audit fees. Prior researches also indicate that client industry characteristics influence audit fees. Therefore, the main objective of this study is to examine whether auditor specialization and client industry characteristics influence audit fees and which one has greater effect. We find evidence that auditor specialization and client industry characteristics both have an influence on audit fees, while client industry characteristics exhibit even greater impacts. Furthermore relative to conventional industries, auditor specialization in high technology industries demonstrates greater value, and contributes to higher audit fees.