| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2018 | 6.35 | 7.72 | 5.66 |
| 2017 | 6.66 | 7.21 | 6.22 |
| 2016 | 6.18 | 6.86 | 5.61 |
| 2015 | 7.56 | 10.49 | 5.64 |
| 2014 | 4.73 | 7.67 | 4.09 |
| 2013 | 5.27 | 6.63 | 4.4 |
| 2012 | 5.15 | 6.28 | 4.4 |
| 2011 | 6.01 | 6.82 | 5.4 |
| 2010 | 9.15 | 11.78 | 7.72 |
| 2009 | 12.83 | 18.29 | 8.06 |
| 2008 | 14.54 | 27.68 | 7.19 |
| 2007 | 32.22 | 40.15 | 24.96 |