中文摘要：

从承销商追求自身利益最大化角度解释我国IPO上市首日是否破发及破发程度。选取2010~2012年深圳中小板和创业板IPO首日破发的116只股票与按1：1配对的非破发股作为样本,分别运用Logistic回归模型和多元回归模型,检验承销商利益最大化行为对IPO是否破发及破发程度的影响。研究发现,承销商在IPO定价时会关注自身短期利益（发行费用）和对发行人（IPO发行规模）的影响,而忽视长期利益（承销商声誉）和对机构投资者（网下有效配售比例）的影响。这一权衡结果会促使承销商最终选择推高发行价格,进而引起并加剧IPO破发。

英文摘要：

This paper tries to explain the IPO overpricing phenomenon based on the theory of underwriters＇ pursuit of maximizing the benefits under book-building system. In order to investigate IPO overpricing, this paper selects the 116 IPO shares overpricing on the first day of listing and the 116 on- IPO overpricing marched shares as samples. The results show that the underwriters are concerned about their short-term interest（underwriting fee）, about the issuers＇ effects（IPO issue size）, while ignoring their long-term interests（underwriter reputation）and institutional investors＇ impact when they decide the IPO price. The trade-offs results will lead underwriter to push up the issue price, thereby causing IPO overpricing.