China’s pilot emissions trading system as a stress test for substantive ESG improvement through green technological innovation

Abstract ESG scores increasingly inform sustainable finance decisions. However, their credibility is often questioned because rating improvements may reflect enhanced disclosure rather than substantive upgrading. This study treats China’s pilot emissions trading system (ETS) as a policy “stress test” for ESG credibility. Under the regulation, carbon costs become binding through monitoring, reporting, verification, and end-of-cycle allowance surrender. Using panel data on China’s A-share listed firms from 2008–2020, this study exploits the staggered rollout of ETS pilots in a multi-period difference-in-differences (DID) framework with firm and year fixed effects, supported by event-study diagnostics and robustness checks including placebo tests, IPW-DID, alternative inference aligned with region-based treatment variation, and cohort-robust modern DID estimators. To assess whether ETS-induced ESG changes reflect substantive upgrading, this study links ETS exposure to green technological innovation (GTI) and quantifies the indirect pathway through GTI using a bootstrapped mediation-style decomposition. The results show that ETS exposure significantly improves firm-level ESG performance and increases GTI, and the mediation estimates indicate a positive indirect pathway through GTI. The GTI-mediated pathway is stronger among firms facing tighter financing constraints and those with more concentrated ownership, highlighting the conditioning roles of financial capacity and internal governance. Overall, this study suggests that ETS regulation induces innovation-driven upgrading that is reflected in ESG outcomes, thereby improving the interpretability of ESG signals and informing the design of compliance and disclosure infrastructure for the low-carbon transition.