The economics of sustainable finance: a comparative analysis of regulatory models for green financial instruments in the jurisdictions of EU, USA, China, and Russia

Recent climate threats and carbon regulation provide the global transformations of the financial system. Therefore, the green bond market is becoming a key indicator of the transition to a post-carbon economy. Consequently, the growth of green financing and a concurrent crisis of trust determine the relevance of the research. Those occurred as a result of fragmented regulatory frameworks, inconsistent taxonomies, and practices of greenwashing. Moreover, they threaten the resilience of the financing ecosystem. The objective of the research is a comparative analysis of regulatory models in the EU, USA, and China, as well as a diagnosis of institutional challenges in Russia and other developing economies. The research purposes are as follows: (1) analysis of the regulatory base; (2) examining the relationships between regulatory stringency and the cost of capital; (3) assessment of verification and disclosure mechanisms; (4) development of an Integral Regulatory Maturity Rating (IRMR) model; (5) recommendations for the adaptation of international best practices. The methodology involves systems and comparative analysis, case studies, expert scaling, and unique coefficients. According to the research results, stringent regulation (EU) ensures transparency but reduces flexibility; market autonomy (USA) stimulates innovation but increases information asymmetry; and centralised incentivisation (China) mobilises resources but diminishes accountability. The following critical institutional deficits were identified for Russia: a low regulatory maturity index (IRMR = 0.48), a fragmented verification infrastructure with an independence coefficient of 0.31, weak integration with international standards (0.46), and insufficient fiscal incentives. The Russian green bond market requires a comprehensive modernisation of its regulatory structure, including harmonisation of the national taxonomy, the establishment of an independent verification system, and more active participation in global sustainable finance initiatives. The practical significance of the work is in proposed development strategy for the Russian green bond market. The scientific novelty consists in an experimental maturity model with non-linear weights and the identification of a paradox: high formal maturity increases transaction costs, forming an inverse relationship between legitimacy and affordability. This research contributes to institutional economics, the theory of information asymmetry, and the political economy of sustainable finance.