| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2019 | 6.19 | 6.84 | 5.71 |
| 2018 | 6.29 | 7.72 | 5.66 |
| 2017 | 6.79 | 7.29 | 6.4 |
| 2016 | 6.23 | 6.95 | 5.68 |
| 2015 | 7.62 | 10.56 | 5.67 |
| 2014 | 4.90 | 7.76 | 4.3 |
| 2013 | 5.49 | 7.27 | 4.51 |
| 2012 | 5.70 | 6.56 | 4.82 |
| 2011 | 7.33 | 8.86 | 5.73 |
| 2010 | 11.14 | 16.08 | 8.4 |
| 2009 | 13.54 | 19.31 | 8.5 |
| 2008 | 14.51 | 26.39 | 7.53 |