| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2025 | 1 | 1.3 | 0.85 |
| 2024 | 0.76 | 1.89 | 0.48 |
| 2023 | 0.65 | 0.77 | 0.57 |
| 2022 | 0.73 | 1.22 | 0.56 |
| 2021 | 0.67 | 0.77 | 0.55 |
| 2020 | 0.93 | 1.19 | 0.76 |
| 2019 | 1.23 | 2.09 | 0.87 |
| 2018 | 1.77 | 3.14 | 0.96 |
| 2017 | 2.79 | 3.65 | 2.02 |
| 2016 | 2.29 | 3.63 | 1.54 |
| 2015 | 2.08 | 3.28 | 1.36 |
| 2014 | 1.24 | 1.53 | 1.07 |
| 2013 | 1.35 | 1.66 | 1.11 |
| 2012 | 1.48 | 1.87 | 1.19 |
| 2011 | 2.27 | 3.14 | 1.47 |
| 2010 | 3.06 | 4.45 | 2.18 |
| 2009 | 3.16 | 4.82 | 1.51 |
| 2008 | 2.85 | 6.41 | 1.24 |
| 2007 | 5.24 | 8.44 | 2.44 |
| 2006 | 2.23 | 2.91 | 1.61 |
| 2005 | 2.07 | 2.86 | 1.5 |
| 2004 | 3.41 | 5.01 | 2.56 |
| 2003 | 4.47 | 5.53 | 3.54 |
| 2002 | 5.33 | 7.02 | 2.53 |
| 2001 | 5.71 | 6.89 | 4.62 |
| 2000 | 4.29 | 5.63 | 3.44 |
| 1999 | 3.19 | 4.5 | 2.43 |
| 1998 | 3.59 | 5.63 | 2.36 |
| 1997 | 5.12 | 7.38 | 3.67 |