Has the Construction of National Intellectual Property Model Cities Reduced PM 2.5 Concentration and Standard Deviation? New Evidence from Counties in China

PM 2.5 poses a serious threat to public health, and stronger intellectual property (IP) protection can help reduce PM 2.5 concentrations. This study treats the rollout of National Intellectual Property Model Cities (NIPMC) as a quasi-natural experiment in IP protection, using an unbalanced panel of 2074 counties from 2005 to 2021. We employ a multi-period difference-in-differences (DID) design to examine how NIPMC affects both average PM 2.5 levels and their variability. Three main findings emerge. First, NIPMC significantly lowers PM 2.5 levels and their dispersion in pilot counties, a result that remains robust across a battery of checks. Second, NIPMC reduces PM 2.5 by strengthening local innovation capacity and by accelerating industrial restructuring and upgrading. Third, the reduction in average PM 2.5 is especially pronounced in areas with weaker IP protection, general (non-core) cities, and in western regions; meanwhile, the reduction in PM 2.5 variability is particularly notable in weak-IP areas, general cities, and central regions. Together, these results provide new evidence on the environmental benefits of IP protection and offer actionable policy guidance for developing countries pursuing cleaner air.