Determinants of the selection of sustainability assurance providers and consequences for firm value: a review of empirical research

This study aims to focus on the determinants and consequences of the selection of different sustainability assurance providers. The analysis is based on the legitimacy theory and the business case argument. The structured literature review includes 52 quantitative peer-reviewed studies on major categories of providers [(Big Four) audit firms, other assurance providers, financial auditors as sustainability assurors and joint audits between audit firms and other assurance providers]. The results of the included studies are either too heterogenous or too scant to stress clear tendencies of significant drivers and consequences for firm value based on the specific choice of a sustainability assurance provider. This aligns with the theoretical framework and the controversial discussion about the benefits of professional accountants versus other external assurance providers. Prior research has mainly concentrated on the selection of (Big Four) audit firms as sustainability assurors, but there are few studies on the combination of financial audits and sustainability assurance, as well as joint audits between audit firms and other assurance providers. Due to recent regulations on sustainability reporting and assurance practices, future studies should address these aspects in more detail. As the reliability of sustainability reports represents a major demand of stakeholders, firms should select high-quality sustainability assurors to increase firm reputation and stakeholder trust. This study adds to previous research by focusing on the selection of sustainability assurors and quantitative studies as the comparability to other related proxies [e.g. the implementation of sustainability assurance, the scope of assurance (reasonable versus limited) or the quality of assurance statements] and other research methods is limited. To the best of the authors’ knowledge, this is the first literature review on this topic, which mainly contributes to the current controversial discussion about the usefulness of professional accountants versus other parties as sustainability assurance providers.