| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2020 | 8.25 | 8.38 | 8.12 |
| 2019 | 8.42 | 9.35 | 7.66 |
| 2018 | 9.19 | 11.46 | 7.95 |
| 2017 | 14.18 | 18.14 | 9.84 |
| 2016 | 9.86 | 16.55 | 6.79 |
| 2015 | 11.2 | 14.96 | 8.37 |
| 2014 | 8.53 | 12.02 | 7.24 |
| 2013 | 9.01 | 10.73 | 7.28 |
| 2012 | 8.81 | 10.15 | 7.43 |
| 2011 | 10.83 | 13.21 | 8.89 |
| 2010 | 16.23 | 24.33 | 11.23 |
| 2009 | 20.8 | 27.32 | 15.1 |
| 2008 | 30.3 | 63.01 | 14.62 |
| 2007 | 47.38 | 69.54 | 34.87 |