| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2025 | 0.96 | 1.02 | 0.91 |
| 2024 | 0.94 | 1.07 | 0.82 |
| 2023 | 1.13 | 1.39 | 0.99 |
| 2022 | 1.2 | 1.67 | 1.05 |
| 2021 | 1.08 | 1.44 | 1 |
| 2020 | 1.17 | 1.43 | 1.08 |
| 2019 | 1.25 | 1.53 | 1.13 |
| 2018 | 1.55 | 2.22 | 1.16 |
| 2017 | 2.48 | 3.12 | 2.04 |
| 2016 | 3.19 | 3.73 | 2.61 |
| 2015 | 5.64 | 11.68 | 2.83 |
| 2014 | 4.6 | 6.96 | 3.38 |
| 2013 | 3.44 | 4.02 | 2.76 |
| 2012 | 3.57 | 4.79 | 2.56 |
| 2011 | 4.18 | 6.1 | 2.65 |
| 2010 | 5.92 | 8.56 | 3.73 |
| 2009 | 4.56 | 6.47 | 3.01 |
| 2008 | 4.53 | 9.18 | 1.95 |
| 2007 | 6.83 | 9.66 | 3.29 |
| 2006 | 2.51 | 4.4 | 1.69 |
| 2005 | 1.68 | 1.89 | 1.39 |
| 2004 | 2.78 | 4.51 | 1.64 |
| 2003 | 3.96 | 4.49 | 3.44 |
| 2002 | 5 | 6.25 | 3.46 |
| 2001 | 6.02 | 7.34 | 4.22 |
| 2000 | 5.77 | 6.87 | 4.26 |
| 1999 | 4.69 | 6.06 | 3.84 |
| 1998 | 7.43 | 13.69 | 3.79 |
| 1997 | 5.93 | 8.72 | 3.94 |