| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2025 | 0 | ||
| 2024 | 0.78 | 1 | 0.58 |
| 2023 | 1.23 | 1.47 | 0.84 |
| 2022 | 1.46 | 1.79 | 1.25 |
| 2021 | 1.59 | 1.86 | 1.19 |
| 2020 | 1.9 | 2.28 | 1.62 |
| 2019 | 2.37 | 3.22 | 1.96 |
| 2018 | 2.69 | 3.69 | 2.01 |
| 2017 | 4.5 | 5.84 | 3.32 |
| 2016 | 8.37 | 15.19 | 5.58 |
| 2015 | 10.51 | 21.86 | 5.6 |
| 2014 | 4.26 | 6.94 | 3.19 |
| 2013 | 3.66 | 4.67 | 2.95 |
| 2012 | 4.53 | 6.13 | 3.48 |
| 2011 | 5.17 | 5.88 | 4.62 |
| 2010 | 6.15 | 8.02 | 4.93 |
| 2009 | 5.17 | 8.56 | 3.05 |
| 2008 | 5.21 | 9.09 | 2.16 |
| 2007 | 7.42 | 10.91 | 2.06 |
| 2006 | 1.98 | 2.98 | 1.12 |
| 2005 | 1.11 | 1.59 | 0.76 |
| 2004 | 2 | 2.91 | 1.42 |
| 2003 | 2.45 | 3.2 | 1.97 |
| 2002 | 4.15 | 5.19 | 2.82 |
| 2001 | 5.85 | 7.08 | 4.23 |
| 2000 | 4.77 | 5.74 | 3.28 |
| 1999 | 3.66 | 5.09 | 2.86 |
| 1998 | 4.58 | 6.03 | 2.91 |
| 1997 | 5.92 | 9.07 | 3.8 |