在過去的文獻裡，關於合資的研究大多著重於合資夥伴的財富效果，及其他與合資動機、利益相關的議題；本研究即是第一份檢視水平合資宣告時，其上游供應商及下游消費者產業財富效果的研究。

本研究有兩個主要的假設，綜效分享與市場力量，根據這兩個主要的假設，繼續向下延伸以產業集中度、公司大小等變數來衡量下游產業的財富效果，以期探討這樣的市場反應該歸因於哪一個假設。本研究的樣本來自於SDC，樣本將涵蓋1989年到1999年的294家曾經宣告水平合資的上市公司，並以事件研究法來探討合資宣告後，上下游產業的股價波動反應。

實證結果發現，合資公司與上下游公司產業的財富效果皆支持綜效分享假設，特別是當樣本再以新設公司作劃分時，綜效分享的效果會更明顯。雖然在迴歸分析時發現產業集中度、公司大小與下游產業的財富效果呈現負向相關，但當我們以同產業的新設公司為子樣本時，綜效分享的強度增強，並支配了市場力量的影響，進而發現當公司規模大、市場競爭時，下游產業反而能獲得正面的影響。因此，我們認為整體的實證結果將支持綜效分享假設。

關鍵字：水平合資，上下游產業

In the past, researches about joint venture usually focus on their partner firms’ wealth effects or some other issues such as motives, benefits in the joint venture. Our research is the first study about customer and suppliers wealth effect when joint venture announce.

In this research, we have two major hypotheses, synergy sharing and market power hypotheses. Then, we use industry concentration, firm size and other control variables to testify our customer industry in order to distinguish which hypothesis we can go through. We contract data from SDC in 294 public-traded sample firms which has announced horizontal joint venture and the sample period is from 1989 to 1999.

Our finding suggests that synergy sharing is more strengthen than market power. For the overall sample, the wealth effect of CAR drive to support synergy sharing especially for the same new venture subsample. In other word, when new venture is in the same industry with joint ventures, they enhance the strength of synergy sharing even dominate the influence of market power. In our cross-sectional analysis of abnormal returns, we find the market competition and firm size could negatively affect the CAR to the customer industry.

However, when we consider the subsample which is in the same industry, the benefit occurred from economies of scale and efficiency result in a very explicit direction that larger firms and competitive market is somehow good for customers. In sum, we conclude our evidences are driven to the synergy sharing hypothesis.

Key words: Horizontal joint venture, customers and suppliers industry.

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