Table 2.
IPS and Breitung panel unit root tests (explanatory variables)
| Variables | Order | IPS test | Breitung t test |
|---|---|---|---|
| ln CO | Level | 1.15244 (0.1246) | 0.44468 (0.6717) |
| 1st Difference | 29.9108 (0.0000)*** | −19.8485 (0.0000)*** | |
| ln SO2 | Level | 0.23003 (0.4090) | 1.12019 (0.8687) |
| 1st Difference | 24.4075 (0.0000)*** | −15.7590 (0.0000)*** | |
| ln NOX | Level | 0.85669 (0.1958) | −1.11860 (0.1317) |
| 1st Difference | 27.5209 (0.0000)*** | −21.6764 (0.0000)*** | |
| ln CO2 | Level | 1.61645 (1.0000) | −1.01383 (0.1553) |
| 1st Difference | 1.45173 (0.0000)*** | −7.19682 (0.0000)*** | |
| lnY | Level | 9.33569 (1.0000) | 5.43386 (1.0000) |
| 1st Difference | 19.7009 (0.0007)*** | −8.11925 (0.0000)*** |
p values are in parenthesis while *** represents 1 % level of significance