| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2020 | 5.66 | 5.88 | 5.42 |
| 2019 | 5.97 | 6.59 | 5.69 |
| 2018 | 6.35 | 7.99 | 5.78 |
| 2017 | 6.57 | 7.73 | 5.8 |
| 2016 | 5.78 | 6.74 | 5.4 |
| 2015 | 7.53 | 9.69 | 6.04 |
| 2014 | 4.74 | 7.13 | 4.37 |
| 2013 | 5.53 | 6.7 | 4.75 |
| 2012 | 6.32 | 7.08 | 5.57 |
| 2011 | 7.94 | 9.71 | 6.57 |
| 2010 | 11.55 | 16.59 | 8.9 |
| 2009 | 15.41 | 20.04 | 10.64 |
| 2008 | 17.74 | 31.27 | 10.82 |
| 2007 | 31.4 | 36.29 | 27.72 |