| Different stationarity tests | The order of differencing | The test statistic values | p-value |
| ADF | 0 | −4.2998 | 0.01 |
| PP | 0 | −11.270 | 0.01 |
| KPSS | 0 | 0.64742 | 0.02 |
| ADF | 1 | −7.305 | 0.01 |
| PP | 1 | −28.292 | 0.01 |
| KPSS | 1 | 0.012779 | 0.10 |