Table 4.
Traditional unit root tests
| At level I(0) | First difference I(1) | Decision | |
|---|---|---|---|
| Intercept & trend | Intercept & trend | ||
| ADF unit root test | |||
| GDP | 0.3979 | − 0.9324* | I(1) |
| CO2 | − 0.9710 | − 8.0537* | I(1) |
| EC | − 0.5678 | − 7.0742* | I(1) |
| GCF | − 4.7370* | − 6.3073* | I(0), I(1) |
| Urban | − 4.9187* | − 2.1810 | I(0) |
| PP unit root test | |||
| GDP | 0.6869 | − 6.9458* | I(1) |
| CO2 | − 0.9463 | − 8.0591* | I(1) |
| EC | − 0.5908 | − 7.0742 | I(1) |
| GCF | − 4.7149* | − 15.3632 | I(0), I(1) |
| URB | − 4.0221** | − 2.6810 | I(0) |
Note: 1% and 5% level of significance is illustrated by * and ** respectively