The Moderating Effect of~Environmental Performance on~the Relationship between Sustainability Assurance Quality and Firm Value: A Simultaneous Equations Approach

Purpose: This study elucidates the interactive relationship of sustainability assurance (SA) quality with corporate environmental sustainability performance (CESP) and firm value and explores the moderating impact of CESP on the SA quality\textendashfirm value relationship. Design/methodology/approach: The sample comprises 320 firm-year observations of 40 companies listed on the Cotation Assistée en Continu (CAC 40) from 2010 to 2019. The authors use the simultaneous equations model to capture the CESP and SA quality\textendashfirm value relationship and apply the three-stage regression and generalised method of moments approaches to address possible endogeneity. Findings: The results show that CESP, as assessed by International Organisation for Standardisation (ISO) 14001 certification, has a significant positive effect on firm value, the relevance of which implies that in the case of good environmental performance, society's perception of a firm is much more favourable; consequently, the firm is likely to be rewarded with a premium value in capital markets. In addition, environmental performance has a stronger interaction with SA quality, acting as a moderator variable; thus, greater SA quality signals credibility owing to increased eco-efficiency. The authors interpret their findings within a multi-theoretical framework that draws insights from legitimacy, stakeholders and signalling theoretical perspectives. Originality/value: This study contributes to the literature by re-examining the relationship between SA quality and firm value. It also provides new evidence of the moderating effect of CESP on the SA quality\textendashfirm value nexus. Specifically, this study explores the joint effects of credibility and eco-efficiency on market confidence in sustainability information. The authors use a simultaneous equation model to capture the reciprocal association between SA quality and firm value, whereas prior studies on SA quality and market performance have frequently used single-equation regression. The authors also find that CESP positively moderates the relationship between SA quality and firm value. Including CESP and exploring the moderating impact of eco-efficiency on the SA quality\textendashfirm value relationship is a novel approach. \textcopyright 2023, Emerald Publishing Limited.