本文建立一個只有兩家廠商的雙占模型，主要參考Creane and Miyagiwa (2009)的文章，考慮廠商成本訊息完全以及訊息不對稱下，在研發會發生成本的假設下，既存廠商的研發策略是否為有效的阻嚇進入策略。 我們發現，不論在成本訊息完全或成本訊息不對稱下，既存廠商的研發策略都不會是阻嚇進入的策略。在有研發的情形，既存廠商都會選擇研發讓新進廠商共存於市場來獲得較高的利潤。 當既存廠商的成本高時，不論在訊息完全或訊息不對稱下，既存廠商進行研發形成雙占都可獲得較高的利潤。而在完全訊息下，當既存廠商的成本低時，不進行研發維持獨占是較好的策略。但在成本訊息不對稱下，因為受到訊息不對稱的影響，對於新進廠商成本的猜測會改變既存廠商的決定。只有當既存廠商成本介於中間時，因為成本被對手已知的不利狀況以及本身生產成本無法抵銷其研發所增加的額外成本，則既存廠商會選擇不研發保持獨占的狀況。當既存廠商成本很低時，能夠負擔起研發成本，既存廠商又會選擇進行研發，歡迎新廠進入。 Based on Creane and Miyagiwa (2009), this paper builds up a simple duopoly model under perfect and asymmetric information on production costs. We want to find that the effect of R&D on deterring entry when R&D strategy incurs cost. We find that R&D is not an effectively entry-deterring strategy. Both in perfect and asymmetric information, if the incumbent adopts R&D strategy, it will accommodate the entrant to obtain a higher profit. Also, when the incumbent has high production cost, using R&D and accommodating new entrant will be a better strategy both in perfect and asymmetric information. However, when the incumbent has low cost, giving up R&D to stay being monopoly will be the best choice in perfect information situation. While in asymmetric information, the incumbent should give up R&D and stay in monopoly when its production cost is at the middle level, and should choose R&D and accommodate entrant when its production cost is at the very low level.
