Assessing the evolution of sustainability assurance practices and quality: a longitudinal study in an international comparative perspective[Évaluation de l'évolution des pratiques et de la qualité de l'assurance en matière de durabilité : une étude longitudinale dans une perspective comparative internationale]

As sustainability reporting has grown in volume and importance (Mbarek and Dao-Le Flecher 2026), there is an increasing demand for external assurance to enhance credibility, to mitigate greenwashing risks, as so as to reduce information asymmetry between management and stakeholders (Dutta and Dutta 2021; O'Dwyer et al. 2011). Previous literature on sustainability assurance (SA) highlighted important evolution of assurance concepts and standards (Gillet-Monjarret and Rivière-Giordano 2017), but also notable gaps in geographical coverage and organizational types (Hazaea et al. 2022). It underscored the diversity of assurance standards and practices, and consequently inconsistencies in scope, procedures and outcomes across contexts (Edwards et al. 2025; Farooq and de Villiers 2019), thus posing a substantive challenge for international convergence and comparability. The objective of this paper is to assess how SA adoption and practices evolve, and how the quality of SA is shaped across time and contexts. Based on an analysis of sustainability assurance reports in a sample of listed companies in France and in the USA over the 2010-2025 period and of semi-structured interviews with auditors, the study makes contributions to the emerging literature on SA by showing how assurance development would impact disclosure quality and sustainability performance.