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.

目次
第一章 緒論1
第一節 研究動機與目的1
第二節 文獻回顧2
第三節 研究方法與架構4
第二章 模型理論6
第一節 基本模型6
第二節 賽局假設7
第三章 廠商之間存在完全訊息9
第一節 既存廠商不進行研發9
第二節 既存廠商進行研發12
第三節 最適均衡解的比較18
第四章 廠商之間存在訊息不對稱21
第一節 既存廠商不進行研發21
第二節 既存廠商進行研發25
第三節 最適均衡解的比較31
第五章 比較分析35
第六章 結論38
參考文獻40

Creane, Anthony, and Kaz Miyagiwa. 2009. Forgoing invention to deter entry. International Journal of Industrial Organization 27 (5) : pp. 632-638. 
D'Aspremont, Claude, and Alexis Jacquemin. 1988. Cooperative and noncooperative R & D in duopoly with spillovers. The American Economic Review 78 (5): pp. 1133-1137.
Gabszewicz, Jean J. and Sougata Poddar.(1997). Demand fluctuations and capacity utilization under duopoly. Economic Theory, 10(1) , pp. 131-146.
Ishida, Junichiro, Toshihiro Matsumura, and Noriaki Matsushima. (2011). Market Competition, R&D and Firm Profits in Asymmetric Oligopoly. The Journal of Industrial Economics, 59(3), pp. 484-505. 
Fahri Karakaya. and Stahl,Michael J. (1989) Barriers to Entry and Market Entry Decision in Consumer and Industrial Good market, Journal of Marketing, 53:pp. 80-91
Toshihiro Matsumura, and Noriaki Matsushima.(2010).When Small Firms Fight Back Against Large Firms in R&D. The B.E. Journal of Economic Analysis & Policy, 10(1) .
Rosen, Richard J. 1991. Research and development with asymmetric firm sizes. The Rand Journal of Economics 22 (3): pp. 411-429.