| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2025 | 0.67 | 0.71 | 0.62 |
| 2024 | 0.64 | 0.75 | 0.55 |
| 2023 | 0.74 | 0.92 | 0.64 |
| 2022 | 0.82 | 1.02 | 0.66 |
| 2021 | 1.05 | 2.12 | 0.8 |
| 2020 | 0.94 | 1.17 | 0.85 |
| 2019 | 1 | 1.21 | 0.87 |
| 2018 | 1.13 | 1.57 | 0.81 |
| 2017 | 1.58 | 1.81 | 1.4 |
| 2016 | 1.6 | 2.27 | 1.34 |
| 2015 | 3.32 | 7.15 | 1.77 |
| 2014 | 1.83 | 2.54 | 1.34 |
| 2013 | 1.51 | 2.22 | 1.02 |
| 2012 | 1.66 | 2.44 | 1.18 |
| 2011 | 2.32 | 3.06 | 1.4 |
| 2010 | 3.44 | 5.56 | 2.32 |
| 2009 | 3.63 | 5.26 | 2.07 |
| 2008 | 3.99 | 9.38 | 1.69 |
| 2007 | 4.93 | 6.46 | 1.59 |
| 2006 | 1.22 | 1.53 | 0.86 |
| 2005 | 1.09 | 1.34 | 0.74 |
| 2004 | 1.44 | 1.86 | 1.14 |
| 2003 | 1.73 | 2.08 | 1.42 |
| 2002 | 2.42 | 2.88 | 1.86 |
| 2001 | 3.69 | 4.3 | 2.64 |
| 2000 | 5.54 | 6.71 | 4.84 |
| 1999 | 5.09 | 7 | 3.86 |
| 1998 | 4.65 | 6.81 | 2.95 |
| 1997 | 4.35 | 5.51 | 3.39 |