Results of the heterogeneity test
| . | Discharge of industrial wastewater . | |
|---|---|---|
| . | Big city . | Small city . |
| digital | − 0.0887*** (0.031) | −0.1300 (0.312) |
| pgdp | − 1.4170*** (0.532) | −9.0344 (46.055) |
| Sq_pgdp | 0.0561** (0.023) | 0.3829 (1.990) |
| population | − 0.2544 (0.250) | 0.8293 (3.172) |
| industrial | 2.9435*** (0.419) | −4.0263 (4.087) |
| expenditure | − 0.1796* (0.104) | −9.1571 (9.999) |
| hum | − 0.0061 (0.025) | −0.0633 (1.132) |
| finance | 1.1210 (2.865) | 1.2044 (26.384) |
| watert−1 | 0.2812*** (0.087) | 0.5171 (0.847) |
| Constant | 14.8261*** (3.601) | 57.2700 (280.910) |
| N | 1,350 | 1,405 |
| AR(2) | 0.2093 | 0.1813 |
| . | Discharge of industrial wastewater . | |
|---|---|---|
| . | Big city . | Small city . |
| digital | − 0.0887*** (0.031) | −0.1300 (0.312) |
| pgdp | − 1.4170*** (0.532) | −9.0344 (46.055) |
| Sq_pgdp | 0.0561** (0.023) | 0.3829 (1.990) |
| population | − 0.2544 (0.250) | 0.8293 (3.172) |
| industrial | 2.9435*** (0.419) | −4.0263 (4.087) |
| expenditure | − 0.1796* (0.104) | −9.1571 (9.999) |
| hum | − 0.0061 (0.025) | −0.0633 (1.132) |
| finance | 1.1210 (2.865) | 1.2044 (26.384) |
| watert−1 | 0.2812*** (0.087) | 0.5171 (0.847) |
| Constant | 14.8261*** (3.601) | 57.2700 (280.910) |
| N | 1,350 | 1,405 |
| AR(2) | 0.2093 | 0.1813 |
Standard error of robustness is reported in parentheses.
*Significance at the 10% level.
**Significance at the 5% level.
***Significance at the 1% level.