How does China's industrial wastewater shadow price evolve? The perspective of spatiotemporal characteristics and differences decomposition.

To provide a reference for reducing the cost of industrial wastewater treatment and alleviate the pressure on water environment governance in China, we use the non-parametric dual evaluation linear analysis framework to estimate the shadow price of China's urban industrial wastewater (IWSP) with consideration of multiple inputs based on the data of 267 cities in China from 2003 to 2016. Then, we investigate the spatiotemporal characteristics of IWSP and analyze its sources of differences. Main conclusions are as follows: (1) Mean of China's urban IWSP increased from 645.54 yuan/ton in 2003 to 5662.64 yuan/ton in 2016, implicating the significant results and increasing difficulty of emission reduction policies. In addition, the Moran's I index of IWSP decreased from 0.056 to 0.002, implicating declining spatial correlation and differentiated green production processes in various regions. (2) From stock perspective, the σ convergence result shows that the IWSP of the country and each region gradually diverges, and the β convergence results from incremental perspective show that the IWSP of a single region tends to converge in a steady state. Furthermore, regions with lower average shadow prices converge faster than regions with higher average shadow prices. (3) Using the Dagum Gini coefficient method, we find that the overall difference of IWSP dropped from 0.5758 to 0.3568. The intra-regional differences in each region continued to decline, as well as inter-regional differences. And the contribution rate of intensity of transvariation has risen from 33.71 to 60.80%, becoming the main reason for the imbalanced distribution of IWSP.