| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2021 | 6.93 | 7.67 | 6.16 |
| 2020 | 6.2 | 7.39 | 5.6 |
| 2019 | 6.87 | 7.62 | 6.12 |
| 2018 | 7.43 | 10.27 | 6.16 |
| 2017 | 6.87 | 8.04 | 5.92 |
| 2016 | 5.51 | 6.22 | 4.94 |
| 2015 | 6.63 | 8.15 | 5.02 |
| 2014 | 4.77 | 7.36 | 4.37 |
| 2013 | 5.62 | 6.74 | 4.68 |
| 2012 | 6.3 | 7.55 | 5.24 |
| 2011 | 8.23 | 9.9 | 6.89 |
| 2010 | 10.78 | 15.36 | 8.22 |
| 2009 | 13.52 | 17.78 | 8.93 |
| 2008 | 12.12 | 27.21 | 8.96 |