| Augmented DF | Phillips-Perron | Order of Integration | |||
| Level | 1st Difference | Level | 1st Difference | ||
| LGDPNON | −0.670 | −6.299*** | −0.646 | −6.299*** | I (1) |
| LREVOIL | −1.537 | −10.224*** | −1.400 | −10.683*** | I (1) |
| LEXP | 0.168 | −12.688*** | 0.325 | −15.333*** | I (1) |