本文首先建立一個具有網路外部性與水平產品差異性這兩種特徵的一般化模型，探討當產品具有網路外部性特徵時，擁有中間要素的既存廠商是否會為了增加自身產品在最終產品市場的競爭優勢，而提高中間要素價格等問題。再者，從社會福利的觀點，分析政府何時該採行垂直分割政策等議題。本文主要結論是：第一、在市場為未完全覆蓋下，當產品的網路外部性愈大時，既存廠商愈有降低中間要素價格的誘因。反之，在市場為剛好完全覆蓋下，當產品的網路外部性愈大時，既存廠商愈有提高中間要素價格的誘因。第二、當網路外部性程度小於某一程度且基本效用夠大時，政府應該實施垂直分割政策，也就是垂直整合可能會讓社會福利減少。
In this paper, I set up a general model which captures the network externalities and horizontal product differentiation in the final good market, and call for a rigorous investigation over different regulation policies. The paper then investigates the impact of the network externalities on input price and social welfare induced by different regulation policies. This paper has the following findings. First, due to network externalities, the incumbent firm could be strategically lowered the input price. Second, it shows that the vertical disintegration policy improves social welfare if the network externalities is relative large.
