當廠商生產最終財必須相互使用到對方所生產的中間財，這樣的關係稱之為共生。本文即討論共生結構的兩個重直整合廠商的行為，以及本國政府面對此一廠商結構如何採取最適的貿易政策。本文以Spencer and Jones（1991）的模型為基礎設立一個兩國模型，本國與外國各擁有一個重直整合廠商。本國廠商與外國廠商各自生產一種中間財，並相互出口到對方以生產最終財。最後本國與外國廠商生產的最終財皆在外國最終財市場銷售。本國政府則對本國廠商，在中間財出口及最終財出口均採取貿易政策。
    本文分別討論廠商面對最終財市場分別為Cournot或者Bertrand競爭之下本國政府將採取的最適貿易政策。最終財市場為Cournot競爭中，我們發現政府不是對本國廠商進行中間財出口補貼和最終財出口課稅，就是對本國廠商進行中間財出口課稅及最終財出口補貼。但在最終財市場為Bertrand競爭之下，本國政府則同時對中間財出口及最終財出口補貼，或是對中間財出口及最終財出口課稅。

The final goods production which are made by the firms who use each other intermediate inputs are called symbiotic production. This paper considers the optimal trade policies under two vertically-integrated firms with symbiotic production. We build up a two-country model based on Spencer and Jones（1991）. Both countries own a vertically-integrated firm. Both two firms produce one kind of intermediate input and use each other intermediate input for producing their final goods. All the final goods of the foreign and the domestic firms are consumed in the foreign final goods market. The domestic government adopts the optimal trade policy to its intermediate input as well as final products exports.
     This paper considers the optimal trade policy under either Cournot or Bertrand competition in the final goods market. Under Cournot competition, the optimal policy by the domestic country may require an export subsidy on intermediate inputs and an export tax on final products, or an export tax on intermediate inputs and an export subsidy on final products, depending on some specific conditions. On the other hand, under Bertrand competition, the optimal policy may require an export tax on both exports, or an export subsidy on both exports, depending on some specific conditions as well.

第一章	導論．．．．．．．．．．．．．．．．．．．．1
   　　第一節    Motivatio　．．．．．．．．．．1
       第二節    文獻回顧　．．．．．．．．．．3
第二章	   共生與Cournot數量競爭之最終財市場　．．．7
       第一節    最終財市場均衡　．．．．．．．10
   　　第二節    中間財市場均衡　．．．．．．．15
　　　第三節　　本國政府最適貿易政策　．．．．23
　　　第四節　　共生與三國模型．．．．．．．．30
第三章	   共生與Bertrand價格競爭之最終財市場．．．34
      第一節    最終財市場均衡　．．．．．．．35
      第二節    中間財市場均衡　．．．．．．．39
      第三節    本國政府最適貿易政策　．．．．44
第四章	   結論與展望．．．．．．．．．．．．．．．51

參考文獻　．．．．．．．．．．．．．．．．．．．．．54

表 目 錄

表一   與中間財價格之關係．．．．．．．．．．．．．48
表二   與最終財價格 與 之關係．．．．．．．．．．．49
表三   與本國政府貿易政策之關係．．．．．．．．．．49

圖 目 錄

圖一  兩國三階段決策模型．．．．．．．．．．．．．． 9
圖二  mA與mB的關係圖．．．．．．．．．．．．．．．．20
圖三  v 的變化對mA與mB之影響．．．．．．．．．．．．21

中文部份

王光正˙邱俊榮（2004）, “垂直相關市場與最適出口貿易政策,”《經濟論文》, 32（2）, 363-391.

王光正˙吳世傑（2005）, “中間財買賣策略與最終財出口補貼政策,”《經濟論文叢刊》,33（1）,33-58.

英文部分

Brander, J. and B. J. Spencer（1985）, “Export Subsides and International Market Share Rivalry”, Journal of International Economics, 18, 83-100.

Eaton, J. and G. M. Grossman （1986）, “Optimal Trade and Industrial Policy under Oligoploy,”Quarterly Journal of Economics, 101, 383-406.

Spencer, B. J. and R. W. Jones（1991）, “Vertical Foreclosure and International Trade Policy,” Review of Economics Studies, 58, 153-170.

Ishikawa, J. and B. J. Spencer（1999）, “Rent-shifting Export Subsidies with an Imported Intermediate Product,” Journal of International Economics, 48, 199-232.

Chen, Y., J. Ishikawa and Z. Yu（2004）, “Trade liberalization and strategic out-souring,” Journal of International Economics, 63（2）， 419-436.

Cournot, A., 1838, “Of the Competition of Producers.” Chapter 7 and “Of the Mutual Relation of Producers,” Chapter 9 in Researches into Mathematical Principles of the Theory of Wealth, translated by Nathanial T. Bacon, New York, 1987.

Carter, M. And Wright, J., 1994, “Symbiotic Production: The case of Telecommunication Pricing,” Review of Industrial Organization, 9 365-378.

Economides, N. and Salop, S., C., “Competition and Integration Among Complements, and Network Market Structure,” The Journal of Industrial Economics, Vol. 40, No. 1, 105-123.

Sonnenschein, H. “The Dual of Duopoly Is Complementary Monopoly: or, Two of Cournot’s Theories Are One,” The Journal of Political Economy, Vol. 76, No. 2, 316-318

Wright, J., 2002, “Access Pricing under Competition: An Application to Cellular Networks,” Journal of Industrial Economics, 50, 289-316.

Brueckner, J.K., 2001, “The Economics of International Codesharing: An Analysis of Airline Alliance,” International Journal of Industrial Organization, 19, 1475-1498.

Brueckner, J.K., 2004, “Network Structure and Airline Scheduling,” Journal of Industrial Economics, 52, 291-314.