| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2025 | 0.83 | 1.14 | 0.59 |
| 2024 | 0.6 | 0.87 | 0.44 |
| 2023 | 0.8 | 1 | 0.68 |
| 2022 | 0.74 | 1.06 | 0.62 |
| 2021 | 0.66 | 0.74 | 0.56 |
| 2020 | 0.83 | 0.91 | 0.71 |
| 2019 | 0.96 | 1.21 | 0.82 |
| 2018 | 1.06 | 1.39 | 0.83 |
| 2017 | 1.53 | 1.95 | 1.22 |
| 2016 | 1.76 | 2.72 | 1.46 |
| 2015 | 2.43 | 4.1 | 1.54 |
| 2014 | 1.27 | 2.15 | 1.05 |
| 2013 | 1.4 | 1.77 | 1.18 |
| 2012 | 1.53 | 1.8 | 1.28 |
| 2011 | 2.01 | 2.52 | 1.31 |
| 2010 | 2.65 | 3.37 | 2.17 |
| 2009 | 2.8 | 3.93 | 1.52 |
| 2008 | 3.01 | 6.84 | 1.17 |
| 2007 | 5.12 | 8.54 | 2.06 |
| 2006 | 1.79 | 2.36 | 1.41 |
| 2005 | 1.65 | 2.42 | 1.19 |
| 2004 | 2.83 | 3.97 | 2.03 |
| 2003 | 3.83 | 4.57 | 2.51 |
| 2002 | 4.31 | 5.08 | 3.08 |
| 2001 | 4.64 | 5.81 | 3.38 |
| 2000 | 4.84 | 6.16 | 4.05 |
| 1999 | 3.96 | 6.43 | 2.26 |
| 1998 | 2.61 | 3.03 | 2.06 |
| 1997 | 4.06 | 6.52 | 2.76 |