| y1 | y2 | y3 | y4 |
y1 | 1.0000 | 0.9941 | 0.9963 | 0.9781 |
y2 | 0.9941 | 1.0000 | 0.9900 | 0.9590 |
y3 | 0.9963 | 0.9900 | 1.0000 | 0.9841 |
y4 | 0.9781 | 0.9590 | 0.9841 | 1.0000 |