| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2025 | 1.63 | 2.09 | 1.34 |
| 2024 | 0.84 | 1.43 | 0.67 |
| 2023 | 1.01 | 1.18 | 0.93 |
| 2022 | 1.08 | 1.72 | 0.91 |
| 2021 | 1.21 | 1.51 | 1 |
| 2020 | 1.8 | 2.18 | 1.42 |
| 2019 | 2.12 | 2.73 | 1.9 |
| 2018 | 2.63 | 4.41 | 2.2 |
| 2017 | 5.47 | 7.04 | 4.33 |
| 2016 | 3.79 | 5.19 | 2.83 |
| 2015 | 2.87 | 5.4 | 1.71 |
| 2014 | 2.13 | 2.56 | 1.85 |
| 2013 | 2.26 | 2.59 | 1.82 |
| 2012 | 2.55 | 2.94 | 2.19 |
| 2011 | 4.21 | 6.12 | 2.32 |
| 2010 | 6.36 | 7.69 | 5.06 |
| 2009 | 5.4 | 7.18 | 3.99 |
| 2008 | 7.26 | 11.24 | 3.35 |
| 2007 | 6.31 | 9.02 | 3.9 |
| 2006 | 2.41 | 4.08 | 1.39 |
| 2005 | 1.35 | 1.56 | 1.14 |
| 2004 | 1.87 | 2.46 | 1.53 |
| 2003 | 2.43 | 3.18 | 1.81 |
| 2002 | 3.65 | 4.25 | 2.34 |
| 2001 | 4.44 | 6.05 | 2.97 |
| 2000 | 4.12 | 5.26 | 2.68 |
| 1999 | 3.21 | 4.93 | 2.27 |
| 1998 | 3.1 | 3.98 | 2.35 |
| 1997 | 3.14 | 4.39 | 2.37 |