| Tear | Sample number | Average value | Standard deviation | min | P25 | P50 | P75 | max |
| 2015 | 2765 | 3.966004 | 1.038479 | 0 | 3 | 4 | 5 | 8 |
| 2016 | 2942 | 3.917063 | 1.124329 | 0 | 3 | 4 | 5 | 8 |
| 2017 | 3397 | 4.053871 | 1.140994 | 0 | 3 | 4 | 5 | 8 |
| 2018 | 3549 | 4.142012 | 1.184552 | 0 | 3 | 4 | 5 | 8 |
| 2019 | 3695 | 4.044655 | 1.351335 | 0 | 3 | 4 | 5 | 8 |
| 2020 | 4058 | 4.082307 | 1.338874 | 0 | 3 | 4 | 5 | 8 |
| 2021 | 4478 | 4.1159 | 1.239371 | 0 | 3 | 4 | 5 | 8 |
| Total | 24,884 | 4.054935 | 1.221351 | 0 | 3 | 4 | 5 | 8 |