The Impact of Intellectual Property Rights City Policy on Firm Green Innovation: A Quasi-Natural Experiment Based on a Staggered DID Model

Green innovation is considered an important way to promote low-carbon society formation and the sustainable development of environmental engineering. However, few quantitative studies have focused on the impact of intellectual property rights (IPR) on firm green innovation (FGI). This paper constructs a quasi-natural experiment based on the IPR pilot city policy in China. We empirically investigated the influence of IPR policy on FGI using a staggered difference-in-differences (DID) model and Chinese listed company data from 2007 to 2020. The findings of this research are as follows: (1) IPR policy significantly promotes FGI, and its effectiveness is confirmed by a variety of robustness tests. (2) The IPR policy supports both green product and green process innovation, with a stronger effect on green product innovation. (3) The IPR policy encourages green independent R&D but has little influence on green joint R&D. (4) The IPR policy promotes FGI with a high knowledge intensity, state-owned enterprises, and firms in key city groups. (5) The IPR policy supports FGI primarily via two institutional channels: increasing R&D investment and easing financing constraints. This paper broadens the study of green innovation city policy and FGI development, offering new perspectives for achieving social and environmental sustainability.