Table 2.
Benchmark results.
| Variables | (1) | (2) | (3) | (4) | (5) | (6) |
|---|---|---|---|---|---|---|
| DID | DID | DID | PSM-DID | PSM-DID | PSM-DID | |
| TR | − 0.516** | − 0.881*** | − 0.867*** | − 0.283 | − 0.612*** | − 0.599*** |
| (− 2.230) | (− 3.770) | (− 3.727) | (− 1.221) | (− 2.665) | (− 2.616) | |
| ln_UR | − 7.404*** | − 7.351*** | − 8.732*** | − 8.514*** | ||
| (− 9.118) | (− 8.979) | (− 9.553) | (− 9.081) | |||
| ln_SO2 | 0.894*** | 0.887*** | 0.929*** | 0.872*** | ||
| (6.034) | (6.265) | (5.795) | (5.515) | |||
| ln_ST | 0.261** | 0.245** | 0.313** | 0.327*** | ||
| (2.223) | (2.150) | (2.513) | (2.666) | |||
| ln_TE | 2.062* | 5.369*** | ||||
| (1.851) | (3.310) | |||||
| ln_SD | − 1.194 | − 1.121 | ||||
| (− 1.515) | (− 1.466) | |||||
| ln_PR | 0.005 | 0.128 | ||||
| (0.031) | (0.751) | |||||
| _cons | 45.685*** | 29.705*** | 33.377*** | 46.059*** | 28.549*** | 22.331*** |
| (571.148) | (20.219) | (4.729) | (565.708) | (17.942) | (2.940) | |
| City-Fixed Effect | Yes | Yes | Yes | Yes | Yes | Yes |
| Year-Fixed Effect | Yes | Yes | Yes | Yes | Yes | Yes |
| Obs | 3976 | 3976 | 3976 | 3841 | 3841 | 3841 |
| R2 | 0.946 | 0.949 | 0.949 | 0.947 | 0.950 | 0.950 |
The t value in parentheses is calculated according to the robust standard error of clustering at the city-year level;
*, ** and ***denotes the significance levels of 10%, 5%, and 1%, respectively.