本研究選取2019年台灣上市櫃非金融業公司之數據為研究樣本，以事件研究法來檢驗康友-KY之舞弊事件發生時，市場上投資人是否會對其他外國來台上市(櫃)企業產生疑慮及擔心，造成其股價下跌，另額外探討康友-KY之會計師事務所查核之外國公司以及康友-KY之簽證會計師查核之外國公司股價是否也受到康友-KY舞弊事件影響，產生股價汙染效果，最後探討公司治理對於汙染效果的影響。
本文結果顯示外國來台上市(櫃)企業之間確實存在股價汙染效果，外國公司受康友-KY舞弊事件影響而有顯著的負向累積異常報酬，而康友-KY之會計師事務所查核之外國公司、康友-KY之簽證會計師查核之外國公司確實也受到康友-KY舞弊事件之股價汙染效果與低審計品質汙染效果影響，同樣有顯著的負向累積異常報酬。本文結果也發現公司治理評鑑等級較佳的公司確實能減緩汙染效果，股價下跌的幅度較公司治理評鑑等級較差的公司少，但康友-KY之簽證會計師查核之外國公司則是沒有得到結果。投資人雖然對外國企業監理環境不佳的情形較沒信心，但是做好公司治理還是能有效緩解市場上投資人的疑慮，受到汙染效果的影響較小。

This study selects the data of Taiwan's listed and OTC non-financial companies in 2019 as the research sample and uses the event study to test when the fraudulent event of Pharmally occurs, whether investors will have doubts and worries in other foreign issuers in Taiwan caused their stock prices to fall. In addition, we further examine foreign companies whose audits conducted by the same audit firm as Pharmally and the same audit partner as Pharmally whether the stock prices of foreign companies were also affected by the fraudulent event of Pharmally, resulting in price contagion effects. Finally, we investigate the impact of corporate governance on contagion effects.
The results show that there is indeed price contagion effect among foreign companies listed in Taiwan. Foreign companies were affected by the fraudulent event of Pharmally and had significant negative cumulative abnormal returns. Foreign companies whose audits conducted by the same audit firm as Pharmally and the same audit partner as Pharmally were indeed also affected by price contagion effects of the fraudulent event of Pharmally and the contagion effect of low-audit quality, and there were also significant negative cumulative abnormal returns. The results also find that companies with better corporate governance evaluation levels can indeed mitigate the contagion effects, and the decline in stock prices is less than that of companies with poor corporate governance evaluation levels. However, foreign companies whose audits conducted by the same audit partner as Pharmally did not yield results. Although investors were less confident about the poor supervision environment of foreign companies in Taiwan, good corporate governance can effectively alleviate investors’ concerns in the market, and they are less affected by the price contagion effects.

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