| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2025 | 2.3 | 2.58 | 2.13 |
| 2024 | 2.14 | 2.84 | 1.76 |
| 2023 | 2.42 | 2.62 | 2.21 |
| 2022 | 2.68 | 3.14 | 2.35 |
| 2021 | 3.11 | 4.1 | 2.5 |
| 2020 | 3.05 | 5.45 | 1.89 |
| 2019 | 2.35 | 2.76 | 2.06 |
| 2018 | 2.47 | 3.12 | 2 |
| 2017 | 4.19 | 5.17 | 3 |
| 2016 | 4.83 | 7.02 | 4.31 |
| 2015 | 5.67 | 10.31 | 3.3 |
| 2014 | 2.9 | 3.93 | 2.28 |
| 2013 | 2.54 | 3.11 | 2.09 |
| 2012 | 2.72 | 3.38 | 2.31 |
| 2011 | 4.11 | 5.34 | 2.58 |
| 2010 | 6.02 | 8.47 | 4.67 |
| 2009 | 4.34 | 6.18 | 3.01 |
| 2008 | 4.4 | 8.09 | 2.55 |
| 2007 | 5.84 | 8.6 | 3.35 |
| 2006 | 3.43 | 4.01 | 3 |
| 2005 | 3.59 | 5.18 | 2.76 |
| 2004 | 4.21 | 5.47 | 3.45 |
| 2003 | 5.81 | 7.21 | 3.83 |
| 2002 | 8.3 | 9.86 | 6.27 |
| 2001 | 11.35 | 15.55 | 6.95 |
| 2000 | 12.95 | 21 | 6.05 |
| 1999 | 6.92 | 9.89 | 4.84 |
| 1998 | 5.73 | 6.99 | 4.36 |
| 1997 | 9.9 | 14.6 | 6.57 |