我国股权分置中对价水平的“群聚”现象分析

从2005年4月29日到2006年3月19日止,上海证券市场共有25批次346家(含29家试点公司)上市公司公布股权分置改革的详细方案。其中高达87.6%股权分置公司的对价水平都集中在10送2至4股区间,平均对价水平为10送3股,对价水平出现显著的10送3股“群聚”现象。本文以不完全竞争市场理论为基础,对上海证券市场346家股权分置公司样本进行实证检验,结果表明,上海证券交易所前25批股权分置公司的保荐市场上,Herfindahl-Hirschman指数(HH指数)平均高达1411,保荐行业的市场准入难度较大,股权分置公司的对价水平与保荐机构所占市场份额显著负相关。证据表明,上海证券市场的保荐行业一定程度上属于寡头垄断,而10送3股的现象可能是寡头垄断的结果,而不是完全市场竞争的结果。

A Study on Clustering of Liquidity Premium of Ownership Restructure in China——Evidences from Shanghai Stock Market

More than 346 listing companies in Shanghai Stock Exchange,including the first 29 used for experiments,declared their ownership restructure scheme from the period of April 29,2005 to March 19,2006.On average,the premium received by public shareholders has a tendency to cluster at 10:3,and more than 87.6% of companies have a premium around the area of 10:2 to 10:4.Theoretically,patterns of clustering can be explained either by the cartel theory or the efficient contract theory.This study conduct an empirical research based on a sample of 346 listing companies in Shanghai Stock Exchange.The result of this test shows that Herfindahl-Hirschman index in the underwriter market of Shanghai Stock Exchange is as high as 1411.Entry Analysis also shows that entry is not that easy in the underwriter market.And there is a significant negative relationship between the premium received by public shareholders and the market shares of investment banks.Overall,the empirical evidence indicated that underwriter market in Shanghai stock exchange is moderately concentrated and the clustering pattern of 10:3 is probably the consequences of collusion among underwriters.