Table 1 Results of principal component analysis
| Factor | Eigenvalue | Proportion of variance | Cumulative variance |
|---|---|---|---|
| 1 | 3.645 | 0.456 | 0.456 |
| 2 | 1.598 | 0.199 | 0.656 |
| 3 | 1.172 | 0.147 | 0.802 |
| 4 | 0.577 | 0.072 | 0.874 |
| 5 | 0.398 | 0.049 | 0.924 |
| 6 | 0.265 | 0.033 | 0.957 |
| 7 | 0.206 | 0.026 | 0.983 |
| 8 | 0.138 | 0.017 | 1 |