3.3.3. Control Variables

Following prior research, we add several control variables to the model, which include: city economic development (LnGDP), city openness (Open), city financial development (Finance), city government scale (Gov), the ratio of city secondary industry (Sec\_Ind), and the ratio of city tertiary industry (Ter\_Ind). Table 1 provides detailed definitions of all variables. The definitions of the main variables are shown in Table 1.

#### **Table 1.** Variables Definition.

