| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2025 | 0 | ||
| 2024 | 0.99 | 1.33 | 0.72 |
| 2023 | 1.09 | 1.52 | 0.85 |
| 2022 | 0.85 | 1.19 | 0.65 |
| 2021 | 0.75 | 0.99 | 0.61 |
| 2020 | 0.78 | 0.91 | 0.66 |
| 2019 | 0.99 | 1.33 | 0.71 |
| 2018 | 0.98 | 1.45 | 0.67 |
| 2017 | 1.73 | 2.53 | 1.27 |
| 2016 | 1.48 | 1.76 | 1.33 |
| 2015 | 2.25 | 3.2 | 1.57 |
| 2014 | 1.57 | 2.91 | 1.17 |
| 2013 | 1.26 | 1.43 | 1.12 |
| 2012 | 1.35 | 1.51 | 1.22 |
| 2011 | 1.6 | 2.06 | 1.26 |
| 2010 | 1.88 | 2.39 | 1.4 |
| 2009 | 2.02 | 2.41 | 1.52 |
| 2008 | 2.32 | 5.07 | 1.14 |
| 2007 | 6.08 | 21.83 | 2.66 |
| 2006 | 2.39 | 2.95 | 1.97 |
| 2005 | 2.78 | 3.89 | 1.98 |
| 2004 | 5.51 | 7.99 | 3.4 |
| 2003 | 6.21 | 6.73 | 5.28 |
| 2002 | 5.65 | 6.77 | 3.92 |
| 2001 | 6.83 | 8.69 | 4.88 |
| 2000 | 6.22 | 7.19 | 4.7 |
| 1999 | 5.24 | 6.99 | 4 |
| 1998 | 4.23 | 5.76 | 3.11 |
| 1997 | 9.13 | 11.99 | 3.75 |