本篇論文主要在探討公司長期表現是否與首次公開上市時向公眾發行的股票比例有關，此比例為發行股數占總流通在外股數的比重，亦即首次公開發行的承銷率。迴歸的結果顯示公司長期表現與承銷率的關係呈現非線性，且當我逐漸增加公司的特徵(如銷售額，淨利及負載比率等)時，非線性的關係仍然存在並更加顯著。台灣市場的樣本顯示長期報酬率與首次公開發行承銷率之間的關係呈現Ｕ字形，意味著當承銷率位於低水平開始增加時，此時公司的長期報酬率會減少。然而，當承銷率從較高的水平上升至更高時，長期的報酬率反而會增加。由此可知，長期表現最好的是在首次公開發行中賣出較少或大部分股票的公司。此現象最好的解釋可以總結為公司的代理問題，公司內部管理階層的激勵誘因與外部監督的力量呈現非線性權衡，也因此造就了公司的長期報酬率與首次公開承銷率之間的二次關係，即前述所提及的Ｕ字形關係。

In this paper, I mainly discuss whether stock long-term performance is related to the percentage of shares which is issued to the public immediately after the date of initial public offering, which refers to public float. The results of regressions in long-term show that the relation is indeed non-linear and still persist when I gradually add firm’s characteristics (such as sales, revenue and debt ratio, etc.). My sample which is obtained from Taiwanese market indicates that the relation between long-run return and public float presents U-shaped. U shaped relation means that when public float increases from a very low level, long-run return will drop. However, long-run return will increase when public float goes from a high level. Thus, firms that have best performance in the long-term are those that have sold fewer or more shares in initial public offerings. The best explanation for the phenomena can attribute to agency problem. I suggest that the quadratic relation between public float and long-run return is due to a non-linear trade-off between insiders’ incentive and the power of public monitoring.

Contents
I. Introduction. 1
II. Literature Review 4
2.1 Return of IPOs in different time interval 4
2.2 Ownership structure and IPO performance 6
2.3 Public float 7
III. Data and Methodology 8
IV. Long-run Return 14
V. Conclusions 27
References 29

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Taiwan Securities Association Rules Governing Underwriting and Resale of Securities by Securities Firms § 21-1h (2016.04.12)