| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2021 | 7.99 | 9.61 | 6.35 |
| 2020 | 8.27 | 9.68 | 7.14 |
| 2019 | 9.27 | 11.2 | 7.78 |
| 2018 | 11.91 | 19.04 | 7.61 |
| 2017 | 12.17 | 15.65 | 9.76 |
| 2016 | 14.55 | 16.73 | 10.27 |
| 2015 | 10.4 | 16.72 | 8.53 |
| 2014 | 6.45 | 9.93 | 5.21 |
| 2013 | 8.84 | 12.53 | 6.29 |
| 2012 | 9.77 | 12.49 | 8.09 |
| 2011 | 12.64 | 17.67 | 10.22 |
| 2010 | 17.36 | 24.72 | 12.91 |
| 2009 | 26.05 | 38.91 | 13.88 |
| 2008 | 29.64 | 79.12 | 10.83 |
| 2007 | 61.99 | 100.07 | 32.92 |
| 2006 | 17.4 | 36.72 | 11.78 |
| 2005 | 11 | 17.96 | 7.48 |
| 2004 | 16.86 | 22.01 | 13.94 |
| 2003 | 16.43 | 20.71 | 14.24 |
| 2002 | 17.48 | 19.47 | 14.92 |
| 2001 | 22.15 | 26.81 | 17.43 |
| 2000 | 26.6 | 34.22 | 18.29 |
| 1999 | 19.95 | 29.15 | 14.3 |
| 1998 | 21.13 | 27.36 | 15.87 |
| 1997 | 26.99 | 38.97 | 16.29 |