本研究以賽局分析的方法，探討網路興起對雙占廠商的產品差異化策略、定價策略與社會福利所造成的影響。本文之產品差異化兼具垂直與水平差異化的特性，即當廠商差異化後會提升部分消費者對產品的評價，並獲致以下結果：(i) 網路興起打破地域藩籬，但未必有害於過去受地域屏障保護的競爭廠商，因為網路興起後廠商進行產品升級、增加產品變化的努力能獲得更多不同地域消費者的青睞，而較多的產品差異化在彌補缺乏地域屏障之餘，甚至可能提升獲利。(ii) 網路興起後，在競爭激化下，迫使廠商更須經由產品差異化來提升消費者毛效用或擴充銷售量，以提升利潤；在某些條件下即便差異化創造的消費者價值不及成本，廠商仍會進行差異化，此時整體社會福利因廠商的過度投資而下降。本研究結果為行銷實務者在網路興起後應如何調整產品差異化與定價策略提供具體建議，亦可為廠商在網路通路的客製化、品牌經營與說服性廣告策略上提供行銷意涵。

This paper takes a game-theoretic approach to analyze how the availability of e-commerce may change duopolistic firms' incentives of engaging in product differentiation, thereby altering equilibrium product prices and social welfare. The migration of transactions from traditional outlets to Internet markets implies that firms that gained local monopoly power in different geographic areas must now compete in one integrated market, but this does not necessarily imply that e-commerce makes firms worse off. We obtain the following results: (i) The presence of internet markets also allows firms to reach consumers that could not be reached in the past because of prohibitively high transportation costs, and the presence of new potential customers raises the profitability of investments in product differentiation. (ii) With products being more differentiated, the equilibrium product prices may become higher, making firms better off in the presence of Internet markets. (iii) The presence of the Internet channel will intensify price competition between firms with homogeneous products, which in turn strengthens their incentives to conduct product differentiation. Under some conditions, even if the value created to customers cannot cover the associated cost, firms may well differentiate their products. In this case, social welfare is decreased by the overinvestment by firms on product differentiation. (iv) Our results provide implications for practitioners on how to adjust their product and pricing strategies in the presence of the Internet. Furthermore, we provide marketing implications for customization, branding and persuasive advertising on the Internet.