本文為探討台灣非金融上市櫃公司之產業集中度變化對公司獲利及營運效率性的影響，使用TEJ資料庫中1981年至2019年台灣所有非金融的上市上櫃公司來進行分析，本研究採用最小平方法及固定效果模型與似不相關迴歸模型(seemingly unrelated regression model)來進行分析。本研究的結果顯示台灣的 Herfindahl – Hirschman index(HHI)是不斷走高的，並發現產業集中度越高的產業，其企業的盈利能力越差，盈利能力較差的原因來自於經營效率降低，這原因可能是產業集中度高使得市場競爭變弱，導致企業忽略經營效率，進而影響盈利能力，我們觀察了各期間的狀況發現這種負面情況主要發生在 1981 年到 2006 年間，不過 2000 年後台灣產業集中度越高的產業，其企業的盈利能力越強，且其原因來自於經營效率提升，這可能是因為 2000 年後，台灣企業去中國設廠，在中國生產能大幅降低成本，也因此企業有了較好的經營效率，進而
影響企業的盈利能力。此外我們還發現併購產業集中度越高的公司並不會有超額的併購利益。而 2000 年後主要公司的營收佔比越高的產業企業的經營效率、產業的經營效率越好，最後我們使用產業集中度高低形成之投資組合進行分析，發現並無法經由此投資方式獲得超額報酬。

To explore the impact of changes in industry concentration on profitability and operational efficiency of non-financial listed companies in Taiwan, we use TEJ database to analyze all non-financial listed companies in Taiwan from 1981 to 2019. In this research, the minimum square method, fixed effect model, and the seemingly unrelated regression model were used. The results of this research show that Taiwan's Herfindahl-Hirschman Index (HHI) is continually rising, and it is found that the higher the industrial concentration, the worse the profitability of the enterprise. The reason for the poor profitability is that the low operational efficiency, which may be due to the weak market competition caused by the high industrial
concentration. Therefore, if the enterprise ignores its operational efficiency, its profitability will be affected. We looked at each period and found that the negative situation mainly occurred between 1981 and 2006. However, after 2000, the industry whose industrial concentration is higher than others in Taiwan has the greater strength of profitability because of management efficiency. After 2000, Taiwanese enterprise set up factories in China, and greatly reduced its production costs, so its operating efficiency was improved, which also affected its strength of profitability. In addition, we also found that it won’t have excess profits after merging or acquiring a company with higher industry concentration. After 2000, when the major companies had higher revenue ratio, its operational efficiency was also
greater. Finally, we use the investment portfolio formed by the level of industrial concentration to analyze, and find that it is impossible to obtain excess returns through this investment method.

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