企業結合雖可提升廠商之競爭能力，但對特定市場亦有可能造成限制競爭或不公平競爭的情形，故世界各主要國家競爭法主管機關均採取管制措施。台灣公平會亦以公平法第12條作為管制的基礎，但尚未完成指導原則加以闡釋。此外，管制之關鍵因素，色括「整體經濟利益」及「限制競爭之不利益」，與水平結合後所產生之「市場績效」關係，及產業別與市場績效之關係如何，現有結合管制文獻均僅有理論性探討尚未發現有採取實證研究加以驗證者。 有鑑於此，本研究乃以台灣自1992年至2004年之水平結合許可案例共158件為樣本，參酌相關理論文獻，經由內容分析法建構整體經濟利益、限制競爭之不利益及市場績效之觀察變數，再藉由SEM、ANOVA及Duncan檢定等分析工具進行驗證。實證結果顯示：(一)整體經濟利益與市場績效間具有正向關係；(二)結合後未產生限制競爭之不利益與市場績效間具有正向關係；(三)整體經濟利益與市場績效間之關係係數大於結合後未產生限制競爭之不利益與市場績效間之關係係數；(四)不同產業的水平結合其市場績效值不同，其中以高科技產業最高，傳統產業最低。前述實證結果與既有的理論文獻相符合，一方面可增進水平結合管制之理論基礎，並對台灣執法實務運用上有所幫助。

It is true that the combining of enterprises, either through merger, acquisition or control, can enhance the overall effectiveness of competition. But at the same time, it may give rise to restrictions or even unfair competition in a particular market. Thus, the competition authorities in most, if not all, developed countries have adopted regulatory measures. The Fair Trade Commission of Taiwan (TFTC) regards Article 12 of the Fair Trade Act (FTA) as the basis for its regulations, but there are no established explanatory guidelines. Hence, two questions arise: What kind of relationships do horizontal combinations produce between the key factors that make up regulations, i.e., the overall economic advantages and the disadvantages resulting from competition restraints and market performance? What is the relationship between different types of industry and market performance? These issues have not previously been examined in any empirical study. Using a research sample of 158 cases of approved horizontal combinations between 1992 and 2004 and conducting a content analysis, this study reviews relevant past documents and constructs observational variables for the overall economic advantages, the disadvantages resulting from competition restraints and for market performance. The empirical analytical methods employed to examine the data include the SEM, ANOV A and the Duncan tests. The results confirm a positive relationship between overall economic advantages and market performance. They also substantiate a positive relationship between disadvantages resulting from competition restraints that are not produced after a horizontal combination is formed and market performance. However, the relationship between the former is stronger than that between the latter. In addition, different industry-types. involved in horizontal combinations have different values of market performance. The hi-tech industry, for example, has the best market performance, while traditional industries have the worst. These empirical results correspond with economic theory and can be used to enhance the theoretical foundation of the Fair Trade Act. These results may also help TFTC in actual situations involving horizontal combinations.