中文摘要：

股改后IPO公司大股东可能存在后市减持的动机。通过对股改前后在A股上市发行的555只新股进行实证研究发现，股改后第2～第10大股东持股比例越高的新股IPO抑价率越高，并且在上市后第13个月的股价相对市场指数下跌的幅度越大，而股改前则不存在这样的现象。研究结果表明，股改后新股大股东在12个月限售期满以后可能存在减持行为，而为了给后市减持提供更高的获利空间，大股东可能拉高新股的首日价格，从而造成了极高的IPO抑价率。

英文摘要：

After the untradable shares reform the major shareholders of IPO companies that issue may sell their shares after market. This paper investigates a sample of 555 IPOs issued and listed in the A-share market before and after the reform, and the empirical results indicate that the total pro- portion of the second to tenth biggest shareholders＇ shares is significantly positively related to the IPO underpricing rate and negatively related to the abnormal return of the thirteenth month after the first day, while that phenomena does not exist before the reform. And these results suggest that the major shareholders may sell their shares in large immediately after the restricted period of 12 months, and in order to obtain higher profits when they sell shares later, they may be incentive to push up the first- day price, which leads to an extremely high IPO underpricing rate.