我国资本市场近年来进入全面注册制改革加速期，在企业首次公开发行上市方面，近年来监管当局也是稳步推进改革措施，我国在2005年之后逐步探索发行人、三方询价机构以及投资者三方竞争博弈的IPO新股发行询价机制。询价机制在前期实施阶段呈现出良好效果，上市企业抑价现象出现一定程度缓解，然而近年来随着中国股票市场全面改革，IPO抑价现象却“卷土重来”且在近两年有了新的形式——“机构抱团压价”，第三方询价机构对创业板上市公司集体压低新股发行价，影响到新股正常定价发行。对此，证监会2021年9月出台创业板市场上市监管新规进行政策放松，引导市场主体回归有序竞争，旨在解决当前火热的机构投资者集体“抱团压价”现象。此政策作为外生事件能否提高一级市场IPO定价效率，能否精准解决机构投资者“抱团报价”现象，从而达到预期监管政策效果——这些根据以往研究无法得出确切结论。因此本文由此入手，从一级市场监管政策角度出发来探寻在当前注册制全面推行背景下，IPO定价效率改善和监管政策实施之间的联系，并且检验此次监管政策是否能够发挥预期政策效应，能否解决当下机构投资者“抱团压价”现象。

本文运用自然实验研究法，使用双重差分模型进行实证研究，对2021年9月证监会监管新规实施前后各一年的创业板和主板两个市场上市企业IPO定价效率进行分析，发现在此次监管新规实施后，创业板新股发行平均抑价率得到一定程度降低。同时，此次监管新规也对机构投资者“抱团压价”现象产生初步改善效应，中介分析模型结论显著成立。此外，通过异质性分析，探究非制度性因素对IPO定价效率机制的影响，得出企业自身特质、二级市场投资者情绪、上市企业所属地域等相关因素在此次IPO定价效率提升机制中发挥的作用，为本研究丰富了新规对IPO新股发行定价效率机制影响的相关观点，其中最为关键的是二级市场因素会对一级市场监管政策效果产生影响，因而为更好地提高IPO定价效率，政府需要在一级市场和二级市场上做好政策配套工作。最后，本文实证研究的结论通过了平行趋势检验、安慰剂检验等检验工具，提高研究结论科学性和有效性。

本文的创新之处在于弥补了以往学者对一级市场定价尤其政策监管部分影响机制的研究不足，更多学者更倾向于二级市场相关因素对定价效率影响，而当下在注册制改革背景之下，政府监管是否能够产生预期政策效应仍然存疑，同时当前机构投资者抱团压价现象具有典型性，因此从理论和实践意义上都是当前股票市场值得研究的课题。当然，在本文研究过程中仍然有部分问题尚存疑问，比如研究的长期效应未检验，新政策在实施后期也许会出现部分新股“破发”现象等，说明此次自然实验的政策效应还需要其他更深入研究工作。

最后，本文基于此次研究发现对监管部门提供建议，包括避免监管政策“一刀切”，因地制宜制定政策，同时提高对机构投资者监管处罚力度、提升自身定价估值能力、完善网下询价制度等等。

In recent years, China's capital market has entered an accelerated period of comprehensive registration system reform. In terms of initial public offering and listing of enterprises, regulatory authorities have also steadily promoted reform measures in recent years. After 2005, China has gradually explored the IPO new stock issuance inquiry mechanism of a tripartite competitive game among issuers, third-party inquiry institutions, and investors. The inquiry mechanism has shown good results in the early implementation stage, and the phenomenon of underpricing by listed companies has been alleviated to a certain extent. However, in recent years, with the comprehensive reform of the Chinese stock market, the phenomenon of IPO underpricing has "returned" and in the past two years, there has been a new form of "institutional group pricing". Third party inquiry institutions collectively lower the issuance price of new shares for companies listed on the Growth Enterprise Board, affecting the normal pricing and issuance of new shares. In response, the China Securities Regulatory Commission (CSRC) released new regulations on the supervision of the listing of the Growth Enterprise Market in September 2021 to relax policies and guide market entities to return to orderly competition, aiming to solve the current hot phenomenon of institutional investors collectively "huddling and pressing prices". Whether this policy, as an exogenous event, can improve the efficiency of IPO pricing in the primary market, accurately solve the phenomenon of institutional investors' 'group bidding', and achieve the expected regulatory policy effect - these cannot be conclusively concluded based on previous research. Therefore, this article starts from the perspective of primary market regulatory policies to explore the relationship between the improvement of IPO pricing efficiency and the implementation of regulatory policies in the context of the comprehensive implementation of the current registration system, and to test whether the regulatory policy can exert the expected policy effect and solve the current phenomenon of institutional investors' "group price pressure".

This article uses the natural experimental research method and a double difference model for empirical research to analyze the IPO pricing efficiency of enterprises listed on the ChiNext and Main Board markets before and after the implementation of the new regulatory regulations by the China Securities Regulatory Commission in September 2021. It is found that after the implementation of the new regulatory regulations, the average underpricing rate of new stock issuance on the ChiNext has been reduced to a certain extent. At the same time, the new regulatory regulations have also had a preliminary improvement effect on the phenomenon of institutional investors' group bargaining, and the conclusion of the intermediary analysis model is significantly valid. In addition, through heterogeneity analysis, the impact of non institutional factors on the IPO pricing efficiency mechanism was explored, and the role of factors such as the company's own characteristics, investor sentiment in the secondary market, and the geographical location of the listed company in the improvement mechanism of IPO pricing efficiency was identified. This enriches the relevant views of the new regulations on the impact of the IPO pricing efficiency mechanism, The most crucial factor is that secondary market factors will have an impact on the effectiveness of regulatory policies in the primary market. Therefore, in order to better improve the efficiency of IPO pricing, the government needs to do a good job in supporting policies in both the primary and secondary markets. Finally, for the conclusions of empirical research, this article also uses robustness testing tools such as parallel trend tests and placebo tests to further validate and improve the scientific and effective nature of the research conclusions.

The innovation of this article lies in making up for the lack of previous research on the impact mechanism of primary market pricing, especially policy regulation. More scholars tend to focus on the impact of secondary market related factors on pricing efficiency. However, in the context of registration system reform, it is still questionable whether government regulation can produce expected policy effects. At the same time, the current phenomenon of institutional investors holding prices together is typical, Therefore, both theoretically and practically, it is a topic worth studying in the current stock market. Of course, there are still some questions in the research process of this article, such as the untested long-term effects of the study, and the possibility of some new stock "breakdowns" in the later implementation of the new policy. This indicates that the policy effects of this natural experiment still require further in-depth research work.

Finally, based on the findings of this study, this article provides suggestions to regulatory authorities, including avoiding the "one size fits all" approach to regulatory policies, formulating policies tailored to local conditions, increasing regulatory penalties for institutional investors, improving their pricing and valuation capabilities, and improving the offline inquiry system.