The influence of sustainability assurance report format and level on nonprofessional investors’ judgments

Purpose This paper aims to examine the influence of sustainability assurance report format (separate versus combined with financial information assurance) and level (limited versus reasonable) on nonprofessional investors’ judgments. Design/methodology/approach This study uses a 2 × 2 between-participants experiment with 436 US nonprofessional investors. The authors manipulate sustainability assurance report format and level to identify differences in judgments of information credibility, investment desirability and investment amount. Findings This study finds that sustainability assurance level influences participants’ judgments only when the financial and sustainability assurance reports are presented separately. Specifically, participants assess sustainability performance information as more credible and make higher investment judgments when presented with a separate limited, as opposed to reasonable, assurance sustainability report. Practical implications The International Auditing and Assurance Standards Board expressed concerns regarding whether assurance reports accompanying emerging forms of extended external reporting (EER) effectively communicate the level of assurance provided by the independent practitioner. The result that assurance level does not influence investor judgments in the combined reporting format appears contrary to the idea that integrated reporting should provide connectivity between financial and sustainability information. The finding that investors make higher investment and credibility judgments with limited assurance is inconsistent with the intent of sustainability assurance professional guidance and recent research results. Together, the findings suggest that investors may not be able to distinguish between differing levels of sustainability assurance when this information is presented in a combined report format. Social implications Standard setters should consider how sustainability assurance report format and assurance level impact nonprofessional investor judgments. Originality/value Research on the effects of EER assurance report format is sparse. The results indicate that even slight changes in assurance report wording may cause investors to perceive that a limited assurance report conveys a higher assurance level than a reasonable assurance report.