| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2025 | 0.97 | 1.23 | 0.79 |
| 2024 | 0.81 | 1.13 | 0.65 |
| 2023 | 0.88 | 1.05 | 0.78 |
| 2022 | 0.92 | 1.11 | 0.72 |
| 2021 | 0.7 | 1.06 | 0.51 |
| 2020 | 0.63 | 0.8 | 0.53 |
| 2019 | 0.76 | 1.05 | 0.63 |
| 2018 | 0.74 | 0.86 | 0.6 |
| 2017 | 1.01 | 1.19 | 0.83 |
| 2016 | 1.17 | 1.54 | 0.99 |
| 2015 | 1.85 | 3.13 | 1.23 |
| 2014 | 1.54 | 1.93 | 1.27 |
| 2013 | 2.19 | 3.3 | 1.72 |
| 2012 | 2.32 | 3.34 | 1.7 |
| 2011 | 4.15 | 6.07 | 2.7 |
| 2010 | 4.33 | 5.86 | 2.68 |
| 2009 | 2.85 | 4.99 | 1 |
| 2008 | 1.58 | 2.77 | 0.8 |
| 2007 | 2.18 | 3.66 | 1.06 |
| 2006 | 1.06 | 1.42 | 0.82 |
| 2005 | 0.94 | 1.22 | 0.76 |
| 2004 | 1.98 | 3.79 | 1.16 |
| 2003 | 3.17 | 4.83 | 2.2 |
| 2002 | 2.58 | 3 | 1.88 |
| 2001 | 3.38 | 4.12 | 2.43 |
| 2000 | 3.63 | 5.55 | 2.83 |
| 1999 | 2.94 | 3.87 | 2.22 |
| 1998 | 3.65 | 5.34 | 2.64 |
| 1997 | 3.46 | 4.69 | 2.46 |