本文旨在討論國外下游廠商將垂直技術移轉納入考慮後，國外廠商進入垂
直市場對社會福利的影響，並進一步放寬下游市場自由進出的假設，探討是否會
對外國廠商的最適技術移轉量有影響，以及地主國下游廠商家數、效率程度等參
數變化時，如何影響社會福利。
本文建立一個垂直相關模型，上游為獨占中間財廠商，提供原料給多家下游最終財廠商，此上游廠商採取單一訂價，下游廠商則將自上游購得之原料投入生產最終財，並在最終財市場上進行數量競爭。此外，有一國外下游廠商具備可以降低原料生產成本之專利技術，並能將技術垂直移轉給本國上游廠商，此外國廠商與上游獨占廠商購買原料後，在最終財市場與本國下游廠商進行數量競爭。本文結果如下，當下游市場無法自由進出時，若外國廠商無技術移轉，則在下游廠商家數少的時候，地主國社會福利會因外國廠商進入而提高，反之，則會使地主國社會福利降低；而當下游市場無法自由進出時，若外國廠商採取最適的技術移轉決策，則外國廠商的進入會使地主國社會福利提高；最後，本文放寬下游市場自由進出的假設，則外國廠商的最適技術移轉量為零，且其進入不會影響地主國的社會福利。

　We hypothesize that multinational firms transfer technology to local suppliers to increase their productivity and to lower input prices. As a result, not just the foreign-owned firm, but all downstream firms of that supply market obtain lower prices. The purpose of this paper is to discuss the impact of foreign manufacturers entering the vertical market on social welfare when the vertical technology transfer is considering. Further relaxes the assumption that the downstream market is free to come in and out to explore whether it will affect the optimal technology transfer decision. As well as the number of the local downstream firm and the degree of efficiency changes how to affect social welfare.
Our model is a three stage game in vertical related market with endogenous vertical technology transfer (VTT). Further, the technology transfer generates an externality that benefits buyers in other sectors downstream from the supply sector as well. This externality may provide a justification for policy intervention to encourage foreign investment. We show that, even though the technology transfer is costly to the multinational firm, the optimal technology transfer decision is positive. When the multinational firm transfer optimal technology to the local supplier, although the local downstream firm faces stronger competition, it obtains the social welfare at better terms. Finally, this article relaxes the hypothesis that the downstream market is free to move in and out, this resulting in the optimal technology transfer decision of foreign firms becomes zero, and its entry does not affect the social welfare of the host country.

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