| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2021 | 31.16 | 41.96 | 25.75 |
| 2020 | 27.63 | 36.49 | 23.1 |
| 2019 | 26.94 | 32.41 | 22.28 |
| 2018 | 29.81 | 38.24 | 22.35 |
| 2017 | 30.23 | 35.87 | 24.9 |
| 2016 | 23.94 | 26.69 | 21.19 |
| 2015 | 28.21 | 36.03 | 23.49 |
| 2014 | 24.3 | 32.56 | 20.4 |
| 2013 | 37.13 | 46.09 | 29.76 |
| 2012 | 30.66 | 34.69 | 26.94 |
| 2011 | 41.43 | 49.39 | 32.54 |
| 2010 | 54.52 | 66.62 | 47.57 |
| 2009 | 44.52 | 56.59 | 36.51 |
| 2008 | 44.1 | 68.43 | 32.92 |
| 2007 | 57.07 | 67.38 | 44.26 |
| 2006 | 35.87 | 48.98 | 25.91 |
| 2005 | 27.07 | 31.66 | 23.56 |
| 2004 | 26.82 | 30.91 | 23.72 |
| 2003 | 28.27 | 43.47 | 22.82 |
| 2002 | 46.47 | 54.68 | 41.49 |
| 2001 | 64.4 | 89.65 | 54.43 |
| 2000 | 77.74 | 91.3 | 56.43 |
| 1999 | 60.69 | 91.71 | 33.27 |
| 1998 | 51.13 | 72.43 | 38.61 |
| 1997 | 40.6 | 55.59 | 32.26 |