整合型市場之下的混合雙占－－價格與數量競爭

Price Competition versus Quantity Competition in a Mixed Duopoly with Integrated Markets

本文在混合雙占模型下，探討由國內與國外消費者所共同組成 之整合型市場中，廠商的內生化競爭策略選擇（數量策略或價格策 略）。研究結果發現：(1) 當商品具有互補關係，或是商品具有替代關 係，且公營廠商的目標函數中對消費者剩餘的權重（國內消費者比 例）大於商品的替代程度時，公營廠商與民營廠商的優勢策略，皆 為選擇價格策略；(2) 當商品具有替代關係，且公營廠商的目標函數 中對消費者剩餘的權重（國內消費者比例）小於商品的替代程度時， 隨著消費者剩餘的權重愈趨不重要，兩家廠商的策略選擇，陸續從 價格策略轉變為數量策略。當消費者剩餘的權重適中時，此模型的 均衡結果會出現，一家廠商選擇數量策略，而另一家廠商選擇價格 策略的混合數量──價格競爭；當消費者剩餘的權重較低時，公營廠 商與民營廠商的優勢策略皆為選擇數量策略。

This paper investigates the theory of endogenous choice of the competition strategy in a mixed duopoly model, in which the public and private firms compete in an integrated market with both domestic and foreign consumers. We present the following findings. First, if the goods are complements, or if the goods are substitutes and the weight of consumer surplus (the fraction of domestic consumers) is greater than the degree of product substitutability, then choosing price is the dominant strategy for each firm. Second, if the goods are substitutes and the weight of consumer surplus (the fraction of domestic consumers) is less than the degree of product substitutability, then the optimal choice of the two firms will gradually change from the price strategy to the quantity strategy. In particular, when the weight of consumer surplus is relatively moderate, mixed quantity-price competition arises as an equilibrium outcome. When the weight of consumer surplus is relatively low, both firms choosing quantity is a dominant strategy equilibrium in a mixed duopoly.