中文摘要：

投资者之间的信息不对称严重影响了市场的有效性．运用买卖价差分解技术，把价差分解成流动性价差和信息不对称价差，比较了它们在B股开放前后的差异，研究了B股向境内居民开放这一事件对市场信息不对称的影响．结论表明，境内居民参与交易虽然增加了股票流动性，但并没有改善市场交易者之间的信息不对称环境．

英文摘要：

The information asymmetry among investors has negative influences on the market efficiency. This paper studies the impact of opening B-share markets to domestic investors on the information asymmetry. We decompose the bid-ask spread into liquidity and information asymmetry components, and then compare their differences in the pre-event and post-event periods. Our results show that the opening event enhances the market liquidity, but doesn＇t mitigate the information asymmetry among the investors.