现代财经(天津财经大学学报)

本文以2015—2023年中国沪深A股上市公司为研究样本，以新《中华人民共和国证券法》(简称《证券法》)修订为准自然实验，运用双重差分法系统检验其对企业层面投资者保护水平的影响及作用机制。研究发现，在监管威慑效应主导下，新《证券法》的实施显著提升了企业层面投资者保护水平，这一结论以会计投资者保护指数作为核心指标得到直接印证，且经系列稳健性检验后依然成立。机制检验表明，新《证券法》主要通过三大路径发挥作用：一是强化法律保护约束，倒逼公司治理优化；二是优化社会监督网络，推动外部审计质量提升；三是激活市场定价效率，优化市场信息生态。异质性分析显示，新《证券法》实施效应在国有企业与科创板和创业板上市企业中更为显著，在投资者管理水平更高的企业和平均受教育年限高的地区中政策效果更具持续性，表明法律政策效应不仅取决于法律威慑力，也取决于政策响应能力。此外，新《证券法》实施还能有效提升企业投资效率、降低股价崩盘风险，为维护资本市场稳定运行提供了制度支撑。本文的研究结论不仅为评估新《证券法》实施效果提供了微观层面的经验证据，也为完善中国特色投资者保护制度提供了理论参考与政策启示。

This paper employs a sample of China's Shanghai and Shenzhen A-share listed companies from 2015 to 2023, utilizing the revision of the new Securities Law of the People's Republic of China(in short, the new Securities Law) as a quasi-natural experiment. A difference-in-differences approach is applied to systematically examine its impact on firm-level investor protection and the underlying mechanisms. The findings reveal that the implementation of the new Securities Law significantly enhances corporate investor protection, primarily driven by regulatory deterrence effects. This conclusion is directly supported by the accounting investor protection index as the core indicator and remains valid after a series of robustness tests. Mechanism tests indicate that the new Securities Law operates through three main channels: First, by strengthening legal protection constraints, which compels corporate governance optimization; Second, by improving the social supervision network, thereby enhancing external audit quality; Third, by activating market pricing efficiency and optimizing the market information ecosystem. Heterogeneity analysis shows that the effects of the new Securities Law are more pronounced in state-owned enterprises and companies listed on the Sci-Tech Innovation Board and ChiNext Board. Additionally, the policy effects exhibit greater sustainability in firms with higher investor management capabilities and in regions with higher average years of education, suggesting that the effectiveness of legal policies depends not only on legal deterrence but also on firms' responsiveness. Furthermore, the implementation of the new Securities Law effectively improves corporate investment efficiency and reduces stock price crash risk, providing institutional support for maintaining capital market stability. The research conclusions of this paper not only offer micro-level empirical evidence for evaluating the implementation effects of the new Securities Law, but also provide theoretical insights and policy implications for improving the investor protection system with Chinese characteristics.