| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2025 | 0 | ||
| 2024 | 0 | ||
| 2023 | 0 | ||
| 2022 | 0 | -0.1 | |
| 2021 | 0 | -0.81 | |
| 2020 | 4.39 | 6.33 | 2.7 |
| 2019 | 5.19 | 7.01 | 3.09 |
| 2018 | 4.66 | 6.55 | 2.91 |
| 2017 | 8.19 | 11.97 | 5.46 |
| 2016 | 11.31 | 15.11 | 8 |
| 2015 | 7.5 | 16.08 | 2.95 |
| 2014 | 2.48 | 3.04 | 1.5 |
| 2013 | 1.77 | 2.18 | 1.4 |
| 2012 | 2.82 | 4.03 | 1.56 |
| 2011 | 3.52 | 4.28 | 2.59 |
| 2010 | 3.48 | 4.55 | 2.32 |
| 2009 | 3.26 | 4.73 | 1.34 |
| 2008 | 2.7 | 5.5 | 1.03 |
| 2007 | 3.83 | 6.15 | 1.59 |
| 2006 | 0.92 | 1.5 | 0.62 |
| 2005 | 0.88 | 1.22 | 0.64 |
| 2004 | 1.57 | 2.12 | 1.13 |
| 2003 | 1.8 | 2.08 | 1.55 |
| 2002 | 2.36 | 2.74 | 1.5 |
| 2001 | 3.1 | 3.66 | 2.32 |
| 2000 | 2.77 | 3.51 | 2.16 |
| 1999 | 2.71 | 3.3 | 2.13 |
| 1998 | 3.58 | 4.42 | 2.99 |