| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2025 | 0.7 | 0.77 | 0.64 |
| 2024 | 0.68 | 0.8 | 0.6 |
| 2023 | 0.79 | 0.83 | 0.73 |
| 2022 | 0.9 | 1.11 | 0.69 |
| 2021 | 1.07 | 1.43 | 0.89 |
| 2020 | 0.98 | 1.15 | 0.86 |
| 2019 | 1.53 | 2.29 | 0.96 |
| 2018 | 2.47 | 3.17 | 1.82 |
| 2017 | 2.88 | 4.09 | 1.8 |
| 2016 | 1.81 | 2.14 | 1.6 |
| 2015 | 2.92 | 4.51 | 1.67 |
| 2014 | 1.89 | 4.09 | 1.43 |
| 2013 | 1.5 | 2.02 | 1.01 |
| 2012 | 1.83 | 2.48 | 1.28 |
| 2011 | 2.92 | 4.13 | 1.7 |
| 2010 | 2.96 | 4.13 | 2.3 |
| 2009 | 2.11 | 3.07 | 1.19 |
| 2008 | 2.2 | 4.37 | 0.88 |
| 2007 | 3.81 | 5.24 | 1.7 |
| 2006 | 1.56 | 1.91 | 1.14 |
| 2005 | 1.32 | 1.86 | 0.94 |
| 2004 | 2.21 | 3.06 | 1.64 |
| 2003 | 2.13 | 2.57 | 1.84 |
| 2002 | 2.5 | 2.79 | 1.82 |
| 2001 | 3.24 | 3.83 | 2.61 |
| 2000 | 3.16 | 4.14 | 2.14 |
| 1999 | 2.33 | 3.53 | 1.5 |
| 1998 | 1.76 | 2.19 | 1.47 |
| 1997 | 1.53 | 2.47 | 1.19 |