Vertical Integration under Product Differentiation

　　本文以一連續雙佔模型(successive duopoly model)，分析當最終財商品異質下，垂直整合對中間財市場、最終財市場、獨立上游廠、獨立下游廠及社會福利的影響。　　我們的研究得到幾個結果：第一，若未垂直整合獨立下游廠所面對的市場規模越小或兩商品的替代性越強時，垂直整合後，越不可能發生中間財的市場封殺(market foreclosure)，獨立下游廠的產量也越可能增加，而此最終財價格也越可能下降。第二，若垂直整合後未發生中間財的市場封殺，獨立上游廠的利潤必定下降。第三，當兩最終財商品為(完全)替代關係時，垂直整合仍可能使獨立下游廠利潤增加；當兩最終財商品為互補關係時，垂直整合仍可能使獨立下游廠利潤減少。第四、垂直整合的進行可能造成社會福利下降。
　　This paper uses a successive duopoly model, under the condition of product differentiation, to analyze the impacts of vertical integration on intermediate goods market and final goods market. It also discusses how vertical integration affects the upstream and downstream firms and social welfare.　　We find the following results. First, the smaller the market size which the nonintegrated downstream firm faces and the more substitutable the two final products are, the less possible it is to encounter market foreclosure after vertical integration. Thus, the production of a non-integrated downstream firm will be larger and the price of final goods will be lower. Second, if market foreclosure for intermediate goods does not happen after vertical integration, the profit of a non-integrated upstream firm will decrease. Third, it is possible for the profit of a non-integrated downstream firm to in crease after vertical integration if the two final goods are (perfect) substitutes; it is possible for the profit of non-integrated downstream firms to decrease after vertical integration if the two final goods are complements. Fourth, it is also possible for social welfare to decrease if the vertical integration takes place.