2.2.2. Energy-Intensive Industries Agglomeration

This paper measures the degree of industrial agglomeration by the number of employees in six energy-intensive industries (chemical raw materials and chemical products manufacturing industry, nonmetallic mineral manufacturing industry, ferrous metal smelting and rolling processing industry, nonferrous metal smelting and rolling processing industry, petroleum processing coking and nuclear fuel processing industry, and power and heat production and supply industry). The calculation formula is as follows:

$$\text{hagg}\_{ij} = \frac{\left(m\_{ij}/m\_j\right)}{\left(M\_i/M\right)}\tag{9}$$

where *mij* is the employment of industry *i* in area *j*, *mj* is the employment of all the industries in area *j*, *Mi* is the national employment of industry *i* and *M* is the employment number of all the industries in the country.

### *2.3. Data Description*

Considering the availability of the data, this paper selected the panel data of 30 provinces in China (excluding Tibet, Hong Kong, Macao and Taiwan) from 2006 to 2017 to verify the relationship between new urbanization, energy-intensive industries agglomeration and NOx emissions and the intermediary effect. The data comes from the China Statistical Yearbook (2007–2018) [62] and China Environment Yearbook (2007–2018) [63,64]. The GDP data used in the variables were calculated at a constant price in 2006 and were processed by using a logarithm. The representation and descriptive statistics of the related variables are shown in Table 2.


#### **Table 2.** Variable description statistics.

#### **3. Results**
