本論文試圖從公司現金持有效率觀點，探討公司治理的內部與外部監督效果。在內部監督方面，從降低代理成本的角度，檢視公司現金持有的使用效率，是否因設置審計委員會，健全公司治理後，而獲得改善。本研究以2007年~2010年設置審計委員會之公司為樣本，使用差異中之差異法，探討審計委員會的監督效果。實證結果顯示，就整體上市櫃公司樣本而言，公司現金持有的價值，未因審計委員的設置而體現出審計委員會應有的監督效果。而進一步依股票交易市場將樣本區分為上市公司及上櫃公司後，上市公司的實證結果顯示，公司現金持有的使用效率，因審計委員的設置而提升；而上櫃公司的現金持有效率則因審計委員的設置而降低。顯示上市上櫃公司的市場結構差異，將使審計委員會的設置對現金持有的使用效率產生不同的干擾效果。 在外部監督方面，Huang and Zhang(2012)的研究發現，在機構投資人為主的美國股票市場，加強資訊揭露，可以降低公司的代理成本，本研究進一步探討以散戶投資人為主的台灣股票市場，資訊揭露是否同樣可發揮資本市場監督與紀律的功能。我們運用Huang and Zhang(2012)的實證模型，驗證在不同的資訊揭露水準下，公司持有現金資產的價值是否存在差異。實證結果顯示，資訊揭露品質較佳的公司，相較於資訊揭露品質較差的公司，其現金資產的價值並無顯著差異， 此與Huang and Zhang(2012) 在以機構投資人為主的市場研究結果並不一致。本研究進一步以機構投資人交易比重， 將樣本區分為機構投資人成交比重高、低兩群，驗證機構投資人及散戶投資人的監督效果是否有所差異，結果顯示，在機構投資人成交比重相對較高的這一組中，資訊揭露程度的高低，確實會影響公司現金持有的價值，兩者呈現顯著正向的關係;而法人成交比重較低的一組，其結果則為無顯著相關。此說明市場提供的外部監督機制，主要由機構投資人進行，因此資訊揭露對公司治理的效果，在以機構投資者為主的證券市場中較為有效。 This study attempted to explore the effects of internal and external supervision of corporate governance from the perspective of a company’s cash holdings efficiency. Internal supervision was examined from the perspective of reducing agency costs, in order to investigate whether the use efficiency of company cash holdings was improved due to the establishment of an auditing committee in which corporate governance was fine-tuned. Companies that established an auditing committee between 2007 and 2010 were included as samples in this study and the difference-in-difference (DID) method was used to explore the supervision effect of auditing committees. Results of empirical analyses showed that generally speaking, within the sample of over-the-counter (OTC) market-listed companies, the expected supervision effect from the establishment of auditing committees was not reflected in the value of companies’ cash holdings. Further empirical analyses were performed after differentiating the sampled companies between Taiwan stock exchange (TWSE)-listed companies and OTC-listed companies, based on the respective stock exchange markets. The empirical results of TWSE-listed companies demonstrated that the use efficiency of company cash holdings increased owing to the establishment of auditing committees, whereas that among OTC-listed companies dropped due to the establishment of auditing committees. These results revealed the differences between the market structures of TWSE- and OTC-listed companies, also indicating that the establishment of auditing committees produced different interference effects on the use efficiency of cash holdings. Huang and Zhang (2012) provide evidence that enhanced information disclosure helps reduce the agency cost from the U.S.A. stock market that is dominated by institutional investors. This study attempts to explore if the supervision and disciplinary effect of capital market still exists in Taiwan’s stock market that is dominated by retail investors. We use the empirical model of Huang and Zhang(2012) to verify whether cash holdings are valued differently depending on information disclosure levels. The empirical results show that the cash holdings of companies with better disclosure quality are not valued significantly higher than those of companies with poorer disclosure quality. This finding is inconsistent with the evidence of Huang and Zhang (2012) from an institutional investor dominated stock market. This study further divides the sample into two sub-samples, one consisting of firms with high institutional trading percentage and the other consisting of firms with low institutional trading percentage, to examine the monitoring effect of institutional and retail investors. Results indicate that for firms with a higher institutional trading percentage, the relation between the product of ratio of change in cash and disclosure level and abnormal returns is significantly positive; for firms with a lower institutional trading percentage, the relation is not significant. This explains the external monitoring in the capital market is mainly provided by institutional investors, and the effect of enhanced disclosure on corporate governance is more pronounced in the stock market dominated by institutional investors.
