Has the Construction of National Intellectual Property Model Cities Reduced PM2.5 Concentration and Standard Deviation? New Evidence from Counties in China

PM2.5 poses a serious threat to public health, and stronger intellectual property (IP) protection can help reduce PM2.5 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 PM2.5 levels and their variability. Three main findings emerge. First, NIPMC significantly lowers PM2.5 levels and their dispersion in pilot counties, a result that remains robust across a battery of checks. Second, NIPMC reduces PM2.5 by strengthening local innovation capacity and by accelerating industrial restructuring and upgrading. Third, the reduction in average PM2.5 is especially pronounced in areas with weaker IP protection, general (non-core) cities, and in western regions; meanwhile, the reduction in PM2.5 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.