As a comprehensive environmental regulation, the low-carbon city pilot policy (LCCP) may have an impact on haze pollution. The evaluation of the effectiveness of LCCP on haze pollution is greatly significant for air pollution prevention and control. Taking LCCP as the starting point, in this study we constructed DID, PSM-DID, and intermediary effect models to empirically test the impact and mechanism of LCCP on haze pollution, based on the panel data of 271 cities in China from 2005 to 2018. The findings show that (1) LCCP has significantly reduced the urban haze pollution, and the average annual concentration of PM2.5 in pilot cities decreased by 14.29%. (2) LCCP can inhibit haze pollution by promoting technological innovation, upgrading the industrial structure, and reducing energy consumption. Among these impacts, the effect of technological innovation is the strongest, followed by industrial structure, and energy consumption. (3) LCCP has significantly curbed the haze pollution of non-resource dependent cities, Eastern cities, and large cities, but exerted little impact on resource-dependent cities, Central and Western regions, and small and medium-sized cities. (4) LCCP has a spatial spillover effect. It can inhibit the haze pollution of adjacent cities through demonstration and warning effects. This study enriches the relevant research on LCCP and provides empirical support and policy enlightenment for pollution reduction.

OEnergy efficiency is a vital factor to promote sustainable development. In this paper, the directional distance function–global Malmquist–Luenberger model (DDF-GML) is applied to measure the energy efficiency levels of 30 provinces in China from 2000 to 2017. Simultaneously, the impacts of the economic growth targets and marketization on energy efficiency are empirically tested using the generalized system moment estimation (SYS-GMM) and mediation effect model. The statistical results reveal that energy efficiency is on the rise every year as a whole. Mediated by marketization, economic growth targets inhibit energy efficiency by distorting marketization. Moreover, there is significant regional heterogeneity in the impacts of economic growth targets on energy efficiency. The inhibition effect of economic growth targets on energy efficiency in the eastern region is greater than in the central and western regions. The above empirical results are determined to be robust through testing.

High-quality economic development relies on industrial transformation and upgrading. To promote industrial transformation and upgrading, efficient fiscal expenditures are undoubtedly important as pillars of national governance. However, in the context of the market economy, the government's excessive intervention in industrial development will lead to the "promotion tournament" of officials and the "beggar-thy-neighbor" local protectionism, resulting in the convergence of regional industrial structure, which will bring uncertain impact on the upgrading of regional industrial structure. Thus, this study empirically assesses how public fiscal expenditure impacts industrial transformation and upgrading as well as the mechanism by developing a spatial econometric model using the panel data of 250 Chinese cities from 2007 to 2020 and further discusses the differential impact from the perspective of urban scale. The findings disclose that public fiscal expenditure serves a crucial role in facilitating industrial transformation and upgrading, but their relationship resembles an inverted U. Therefore, an optimal scale of public fiscal expenditure exists. Heterogeneity findings reveal that the promoting effect of public fiscal expenditure on industrial transformation and upgrading decreases with the expansion of the city scale. The role mechanism implies that public fiscal expenditure indirectly leverages industrial transformation and upgrading through promoting technological innovation, reducing resource dependence, and expanding scale economies. The conclusion provides a theoretical and practical framework for the government to optimize public fiscal expenditure, promote the transformation and upgrading of China's industrial structure, and ultimately attain high-quality development.

Digitization and greening are the vital driving force of China’s economic transformation. Whether they can drive collaboratively China’s economy is the key to realizing sustainable development. In this study, a super efficiency EBM model is applied to calculate the urban green economy development (UGED) level of 266 Chinese cities between 2011 and 2020, and then the dynamic SDM and intermediary effect models are employed to explore the impact and transmission mechanism of digital economy on UGED. Furthermore, it is also investigated whether digital economy and UGED have a nonlinear relationship. In the findings, digital economy is capable of significantly boosting UGED in the local city and its neighborhood, but significant differences exist in different regions and economic development stages. As a result of the transmission mechanism test, it may be found that digital economy could indirectly boost UGED through technology, structure, and allocation effects. The impact of digital economy on UGED has a double threshold due to the significant difference in the urban economic development level. The digital economy is increasingly contributing to UGED as the local economy develops. Therefore, local governments should develop digital economy in line with the local conditions so that its engine role in driving UGED can be given full play.