Board attributes and companies' choice of sustainability assurance providers

We study whether and how the monitoring quality of the board of directors is associated with the choice of providers of assurance for sustainability disclosures. We also examine whether this relation depends on companies' economic, legal, and social environment. In an international empirical study considering five categories of assurance providers, we find that key board attributes, including board size, frequency of board meetings, CEO separation, proportion of women on the board, and the existence of a sustainability committee affect the type of assurance provider chosen by companies. Overall, companies with higher board monitoring quality are more likely to appoint a Big 4 assurer for their sustainability disclosures. Companies with a sustainability committee are more likely to engage an engineering firm, while firms with more board meetings are more likely to appoint an expert assurer. Moreover, we find that companies based in countries with strong environments are more likely to engage an external assurance provider, particularly a Big 4 assurer or an engineering firm. Overall, our results indicate that international sustainability disclosure assurance choices depend on corporate governance practices, as well as countries' economic, social and legal environment.