| Variable | KPSS test value* | Difference order | 1% critical value | 5% critical value | 10% critical value | Test results |
| CS | 0.358 | Zero-order | 0.216 | 0.146 | 0.119 | Smooth |
| XFS | 0.500 | Zero-order | 0.216 | 0.146 | 0.119 | Smooth |
| ZZS | 0.166 | Zero-order | 0.216 | 0.146 | 0.119 | Smooth |
| YYS | 0.164 | First order | 0.216 | 0.146 | 0.119 | Smooth |
| QYS | 0.397 | Zero-order | 0.216 | 0.146 | 0.119 | Smooth |
| GS | 0.374 | Zero-order | 0.216 | 0.146 | 0.119 | Smooth |