Uncovering the Impact of the “Zero-waste City” Pilot Policy on Urban Green Innovation Efficiency

Addressing environmental challenges throughout urban development can spur green innovation. Despite its central role in solid-waste governance, the Zero-waste City initiative’s effects and mechanisms for urban green innovation remain unclear. This study quantifies the causal impact of China’s Zero-waste City pilot on urban green innovation efficiency (GIE). Using a panel of 252 prefecture-level cities (2012–2022), we construct a city-level GIE index via a super-efficiency slack-based measure (SBM) and designate the 11 first-batch pilots as the experimental group. From the remaining cities, we select 39 comparable controls using a propensity-score matching (PSM) model based on six pre-policy covariates, including GIE, economic development, foreign investment, population density, industrial structure, and urbanization. Policy effects are evaluated with a difference-in-differences (DID) model, complemented by six robustness checks. Mechanisms of policy-driven GIE promotion are further examined using patent application counts and the frequency of “Zero-waste City”-related terms in government work reports.

在城市发展全流程中应对环境挑战，可激发绿色创新。尽管无废城市（Zero-waste City）倡议在固体废物治理中居于核心地位，但其对城市绿色创新的影响与作用机制仍有待厘清。本研究量化了中国无废城市试点对城市绿色创新效率（Green Innovation Efficiency，GIE）的因果效应。基于2012-2022年252个地级市的面板数据，本研究通过超效率松弛基测度（Slack-Based Measure，SBM）构建城市层面绿色创新效率指数，并将首批11个试点城市设为实验组。研究从剩余城市中，以绿色创新效率、经济发展水平、外商投资、人口密度、产业结构及城市化水平这6项政策前协变量为依据，通过倾向得分匹配（Propensity Score Matching，PSM）模型筛选出39个可比对照组。本研究采用双重差分（Difference-in-Differences，DID）模型评估政策效应，并辅以6项稳健性检验。进一步通过专利申请量与政府工作报告中"无废城市"相关术语的提及频次，探析政策推动绿色创新效率提升的作用机制。