| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2020 | 7.96 | 8.19 | 7.71 |
| 2019 | 8.48 | 9.45 | 7.36 |
| 2018 | 9.43 | 13.9 | 7.69 |
| 2017 | 14.26 | 20.48 | 9.88 |
| 2016 | 17.8 | 24.25 | 10.89 |
| 2015 | 11.7 | 16.28 | 8.52 |
| 2014 | 6.77 | 9.69 | 5.71 |
| 2013 | 8.09 | 10.68 | 6.56 |
| 2012 | 10.6 | 13 | 8.69 |
| 2011 | 14.02 | 17.12 | 11.12 |
| 2010 | 16.63 | 23.82 | 13.28 |
| 2009 | 22.18 | 29.24 | 15.35 |
| 2008 | 32.79 | 51.16 | 13.89 |