| Variable name | First-Tier and Second-Tier Cities | Other Cities | ||
| OLS | 2SLS | OLS | 2SLS | |
| City size | −0.0616 | −0.803** | 0.849* | 2.294*** |
| (−1.39) | (−2.11) | (1.94) | (3.17) | |
| Square of city scale | 0.0112** | 0.0531** | −2.302*** | −4.507*** |
| (2.31) | (2.44) | (−4.48) | (−4.32) | |
| Environmental pollution | −6.683 | −43.78** | 1.707 | 2.171 |
| (−1.17) | (−2.35) | (0.56) | (0.55) | |
| Interaction between urban scale and environmental pollution | 0.0931 | 8.580** | −9.552 | −13.12 |
| (0.09) | (1.97) | (−0.40) | (−0.41) | |
| Intercept term | 3.686*** | 3.841*** | 2.886*** | 2.754*** |
| (12.43) | (11.77) | (13.01) | (11.90) | |
| control variable | Yes | Yes | Yes | Yes |
| Adjusted R2 | 0.1320 | - | 0.1935 | - |
| Observation value | 2920 | 2920 | 3097 | 3097 |