本研究提出一個量化模型來衡量影響產業獲利程度的四種競爭作用力，即 運用競爭者侷限來衡量現有競爭者之間的競爭態勢、藉由供應商侷限來衡量供 應商議價能力、利用客戶侷限來衡量客戶議價能力、最後採用結構同位侷限來 衡量潛在競爭者與替代品的威脅。接著以台灣產業結構作為實證資料來源，加 以驗證此量化模型之可行性。實證結果顯示這四種競爭作用力對於產業的獲利 程度具有顯著影響，換言之，本研究所提出之量化模型，可以用來衡量競爭作 用力並且比較他們之間的大小，以及評估各個競爭作用力對產業績效的影響程 度。實證結果發現，影響台灣製造產業績效的競爭作用力強度大小依序為結構 同位侷限、競爭者侷限、客戶侷限、供應商侷限。

This study proposes a quantitative methodology for measuring the four competitive forces which affect industry profitability. More precisely, the proposed model uses the competitor constraint to measure rivalry among existing competitors, the supplier constraint to measure bargaining power of suppliers, the buyer constraint to measure bargaining power of buyers, and the structural equivalence constraint to measure threats of new entrants and substitutes. Then, this study empirically examines a sample of industry structures taken from Taiwan. The analytical results show that the four competitive forces indeed have statistically significant influences on industry profitability. Particularly, the model can quantitatively measure and compare the strength of the competitive forces that drive competition within industries, and estimate the impact of these forces on industry performance. The empirical results show that the sequence of the strength of the competitive forces that govern industry performance in Taiwanese manufacturing sectors is structural equivalence constraint, competitor constraint, buyer constraint, and supplier constraint

The first step of formulating competitive strategy is relating a company to its industrial environment. Forces inside and outside the industry have strong influences in determining the competitive strength of the game as well as the potential profit in the industry. Among the industrial organization theory, the competitive forces model proposed by Michael Porter is the most widely known and used framework. This model employs five competitive forces, i.e. rivalry among existing firms, bargaining power of suppliers, bargaining power of buyers, threat of new entrants, and threat of substitute products or services, to evaluate the competitive strength and the potential profit of an industry. All five competitive forces jointly determine the intensity of industry competition and profitability, and the strongest force or forces are governing and become crucial from the point of view of strategy formulation. Both the teaching of strategy management in business schools and the practice of business strategy in business communities apply the competitive forces model as a tool for industry analysis. Although the model is widely used, it is always exercised in a qualitative way and lacks quantitative methods, making it difficult for users to adopt related quantitative approaches to identify which competitive force governs industry competitive strength and determines industry profitability. This study proposes a quantitative methodology for measuring the four competitive forces which affect industry profitability. More precisely, the proposed model uses the competitor constraint to measure rivalry among existing competitors, the supplier constraint to measure bargaining power of suppliers, the buyer constraint to measure bargaining power of buyers, and the structural equivalence constraint to measure threats of new entrants and substitutes. Then, this study empirically examines a sample of industry structures taken from Taiwan. The analytical results show that the four competitive forces indeed have statistically significant influences on industry profitability. Particularly, the model can quantitatively measure and compare the strength of the competitive forces that drive competition within industries, and estimate the impact of these forces on industry performance. The model proposed in this study can help strategy makers in companies formulate competitive strategy and make the decision of entering or exiting a certain industry.