The quality of sustainability assurance reports: The expertise and experience of assurance providers as determinants

The aim of this study was to evaluate the quality of sustainability assurance reports and some aspects associated with it: expertise (a practitioner attribute) and experience (a characteristic of the contractual relationship). Specifically, it examines the impact of the assurance provider's expertise and experience on assurance quality, measured through an index based on a content analysis approach with items related to the reporting format, assurance procedures, and recommendations and opinions. This paper also examines the moderating effect of the type of assurance provider on these relationships. For a sample of international listed companies from the period 2007–14, our evidence shows greater quality of assurance reports when the assurers are industry specialists than when they are nonspecialists, because of their strong industry knowledge, and when the assurers have greater experience in the assurance market because of the extended length of the assurer–client relationship. In addition, the higher quality associated with industry expertise and experience is increased when assurance providers are also accounting firms, given their greater skills and training within the audit profession.