| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2018 | 5.64 | 7.05 | 4.85 |
| 2017 | 6.30 | 6.91 | 5.75 |
| 2016 | 6.95 | 7.51 | 6.26 |
| 2015 | 7.25 | 8.49 | 5.91 |
| 2014 | 5.05 | 8.34 | 4.43 |
| 2013 | 6.27 | 7.86 | 5.08 |
| 2012 | 4.65 | 5.94 | 4.13 |
| 2011 | 5.43 | 6 | 4.73 |
| 2010 | 8.54 | 10.22 | 7.55 |
| 2009 | 10.61 | 14.65 | 6.28 |
| 2008 | 16.38 | 29.78 | 9.29 |
| 2007 | 27.67 | 40.25 | 15.42 |
| 2006 | 12.93 | 27.59 | 7.55 |