Table 5.
Robustness test
| (1) | (2) | (3) | (4) | (5) | (6) | |
|---|---|---|---|---|---|---|
| 14 days after each of the lockdown dates only | Drop firework days | Non-Hubei cities | Cities in Hubei province | AQI level | The dynamic panel data model | |
| ln(AQI_lag) | 0.504*** | |||||
| (115.355) | ||||||
| ln(Migration)*Lockdown | − 0.204*** | − 0.126*** | − 0.114*** | − 0.342*** | − 4.320*** | − 0.058*** |
| (− 5.240) | (− 9.624) | (− 8.322) | (− 3.306) | (− 10.618) | (− 5.212) | |
| Temperature | 0.003*** | 0.002*** | 0.002*** | 0.002*** | 0.105*** | 0.001*** |
| (11.065) | (34.937) | (34.025) | (7.023) | (20.085) | (24.988) | |
| Wind_Direction | − 0.026 | − 0.031*** | − 0.025*** | − 0.076*** | − 0.026*** | − 0.004 |
| (− 1.234) | (− 4.687) | (− 3.678) | (− 2.630) | (− 6.645) | (− 0.606) | |
| Wind_Speed | − 0.175*** | − 0.083*** | − 0.099*** | 0.051 | − 0.182*** | − 0.107*** |
| (− 8.265) | (− 12.689) | (− 14.758) | (1.527) | (− 8.905) | (− 18.820) | |
| Precipitation | − 0.037*** | − 0.044*** | − 0.045*** | − 0.032*** | − 0.277*** | − 0.038*** |
| (− 11.605) | (− 40.258) | (− 39.823) | (− 5.740) | (− 18.941) | (− 39.110) | |
| R2 (within) | 0.991 | 0.993 | 0.993 | 0.997 | 0.852 | 0.995 |
| No. of cities | 5083 | 37,532 | 36,980 | 1472 | 38,744 | 36,885 |
| Observations | Yes | Yes | Yes | Yes | Yes | Yes |
| City FE | Yes | Yes | Yes | Yes | Yes | Yes |
| City by date trend | Yes | Yes | Yes | Yes | Yes | Yes |
| ln(Migration) by date trend | Yes | Yes | Yes | Yes | Yes | Yes |
Standard errors are clustered at the city-day level. t statistics are reported below the coefficients in parentheses
The dependent variable is ln(AQI) in columns (1) to (4) and column (6). ln(AQI_lag) represents the ln(AQI) with 1 day lag
***Significant at 1%
**Significant at 5%
*Significant at 10%