Heterogeneous firm responses to a soft greenhouse gas disclosure regime: evidence from Hong Kong

Purpose This study examines how firms respond to Hong Kong's 2017 greenhouse gas (GHG) disclosure requirement, a soft disclosure regime implemented on a comply-or-explain basis. The paper focuses on whether post-rule patterns differ between firms that voluntarily disclosed GHG emissions before the requirement and firms that disclosed GHG information for the first time after its introduction. Design/methodology/approach The study uses a sample of Stock Exchange of Hong Kong-listed firms subject to the 2017 GHG disclosure requirement and distinguishes between prior voluntary disclosers and first-time disclosers. Using a difference-in-differences design combined with propensity score matching, the paper examines three outcome domains: GHG emissions, selected operating and financial outcomes and reporting-related measures based on accrual-based and real-activity-based earnings management proxies. Additional analyses assess covariate balance, sample attrition, imputation validity, placebo tests and alternative emissions specifications. Findings The emissions analysis provides limited exploratory evidence of immediate short-run reductions in reported GHG emissions for either prior voluntary disclosers or first-time disclosers. Because observed pre-rule emissions are unavailable for first-time disclosers and most comparison firms, the emissions results rely partly on model-based estimates and should be interpreted cautiously. First-time disclosers exhibit more pronounced post-rule changes than prior voluntary disclosers in selected operating and financial outcomes, although these results are tentative because identification diagnostics are not uniformly supportive. The clearest evidence of heterogeneity appears in selected real-activity-based reporting measures, particularly abnormal operating cash flows and abnormal gains on asset sales. These patterns are consistent with reporting-related responses to increased ESG visibility and compliance burden, although they may also reflect genuine operating adjustments rather than opportunistic manipulation. Originality/value The paper contributes to the environmental disclosure and accounting literature by providing evidence from Hong Kong's soft GHG disclosure regime, an underexamined Asia-Pacific setting. By distinguishing between prior voluntary disclosers and first-time disclosers, the study highlights the role of disclosure readiness in shaping firm responses to sustainability reporting regulation. The findings suggest that, under a soft disclosure regime, heterogeneous short-run responses may appear more clearly in reporting-related operating measures than in immediate emissions reductions.