本文考慮一上游獨占、下游同質寡占的市場結構。給定數量競爭，下游廠商進入市場所需支付的固定成本決定均衡的下游廠商家數。由於下游廠商家數的增加會促進下游競爭、減少雙重加價，從而提升上游獲利，本文分析上游廠商補貼下游進入的條件，並探討其福利效果。研究發現，在離散家數的假設下，當下游廠商進行 Cournot 競爭時，由於上游廠商無法藉由線性訂價攫取所有因競爭所帶來的福利利得，補貼後的下游均衡家數小於或等於社會最適的家數，且社會福利隨進入成本上升而下降。相對的，當上游廠商可將下游區分為Stackelberg 領導者以及追隨者兩類廠商時，因應進入成本的變化，上游廠商可藉由調整兩類廠商的相對家數以極大化利潤。此時，社會福利與進入成本間不再存在單調關係。

The research considers a market structure with an upstream monopoly and homogeneous downstream oligopoly. Under quantity competition, fixed entry costs required for downstream firms determine the equilibrium number of firms. As the number of downstream firms increases, it intensifies downstream competition and reduces double mark-up, which consequently enhances profits of the upstream firm. The research analyzes the conditions for the upstream firm to subsidize the entry of downstream firms and investigates its welfare consequences. Assuming the numbers of firms are discrete, when downstream firms engage in Cournot competition, the upstream firm cannot capture all the welfare gains from the enhanced competition through linear pricing. The equilibrium number of downstream firms with subsidization is no greater than the social optimum, and the social welfare decreases as entry costs rise. In contrast, when the upstream firm can separate downstream firms into Stackelberg leaders and followers, it can adjust the relative numbers of these two types of firms in response to changes in entry costs to maximize its profits. Then, a monotonic relationship between social welfare and entry costs no longer exists.

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