| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2025 | 0 | ||
| 2024 | 0 | ||
| 2023 | 0.4 | 0.55 | 0.27 |
| 2022 | 0.51 | 0.62 | 0.41 |
| 2021 | 0.66 | 0.97 | 0.54 |
| 2020 | 0.9 | 1.16 | 0.7 |
| 2019 | 0.95 | 1.29 | 0.77 |
| 2018 | 1.12 | 1.36 | 0.76 |
| 2017 | 1.58 | 1.9 | 1.19 |
| 2016 | 1.8 | 2.38 | 1.53 |
| 2015 | 2.73 | 5.59 | 1.62 |
| 2014 | 1.23 | 1.62 | 1.01 |
| 2013 | 1.2 | 1.6 | 0.96 |
| 2012 | 1.17 | 1.43 | 0.95 |
| 2011 | 1.48 | 1.93 | 1.13 |
| 2010 | 1.95 | 2.55 | 1.46 |
| 2009 | 2.14 | 2.97 | 1.05 |
| 2008 | 2.71 | 8.24 | 0.81 |
| 2007 | 6.38 | 9.6 | 3.01 |
| 2006 | 2.66 | 3.73 | 1.46 |
| 2005 | 1.73 | 2.89 | 1.02 |
| 2004 | 3.22 | 5.09 | 2.39 |
| 2003 | 3.33 | 3.93 | 2.55 |
| 2002 | 4.03 | 5.68 | 3.49 |
| 2001 | 6.78 | 9.2 | 4.56 |
| 2000 | 6.87 | 8.19 | 3.25 |
| 1999 | 3.96 | 5.49 | 3.31 |
| 1998 | 6.07 | 7.41 | 4.52 |
| 1997 | 6.35 | 10.05 | 4.59 |