This study examines in the Spanish setting whether, after the passing of the European Directive 2014/95/UE, investors value positively the voluntary assurance of sustainability reports corresponding to the period 2014–2017 for a sample of listed companies. It also analyzes the valuation by investors of a series of assurance characteristics such as its quality, level of application (reasonable/high vs. moderate/limited), scope (complete vs. partial), and the type of assurance provider (accounting vs. non-accounting firms). Our results find that investors reward firms that adopt external sustainability assurance. Furthermore, we document that investors value to a greater extent those assurance statements with a broader scope, a high/reasonable level of assurance, and with a better quality. Our results are relevant for companies, investors, regulators, and practitioners, and justify the pertinence of the recent Law 11/2018 that places Spain as a European reference by requiring a mandatory assurance of sustainability information in order to increase its reliability and comparability.

中文翻译：

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投资者是否重视可持续性信息的自愿保证？来自西班牙股市的证据

本研究以西班牙为背景，检验了在欧洲指令 2014/95/UE 获得通过后，投资者是否积极评价与 2014 年至 2017 年期间的上市公司样本相对应的可持续发展报告的自愿保证。它还分析了投资者对其质量、应用水平（合理/高vs.中等/有限）、范围（完全vs.部分）和担保提供者类型（会计vs.非会计师事务所）。我们的结果发现，投资者会奖励采用外部可持续性保证的公司。此外，我们记录了投资者在更大程度上重视范围更广、保证水平高/合理且质量更好的保证声明。我们的结果与公司、投资者、