| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2025 | 0.79 | 0.84 | 0.72 |
| 2024 | 1.01 | 1.33 | 0.71 |
| 2023 | 1.24 | 1.74 | 0.84 |
| 2022 | 1.04 | 1.35 | 0.83 |
| 2021 | 0.85 | 1.18 | 0.72 |
| 2020 | 0.75 | 1 | 0.63 |
| 2019 | 0.84 | 1.1 | 0.72 |
| 2018 | 1.04 | 1.34 | 0.8 |
| 2017 | 1.33 | 1.52 | 1.14 |
| 2016 | 1.44 | 1.83 | 1.23 |
| 2015 | 2.51 | 5.32 | 1.27 |
| 2014 | 2.45 | 2.96 | 2.09 |
| 2013 | 3.02 | 4.15 | 1.55 |
| 2012 | 4.71 | 6.47 | 1.29 |
| 2011 | 6.3 | 8.21 | 4 |
| 2010 | 6.3 | 8.22 | 4.19 |
| 2009 | 6.03 | 8.81 | 2.91 |
| 2008 | 6.19 | 11.41 | 2.28 |
| 2007 | 7.96 | 12.35 | 4.32 |
| 2006 | 5.6 | 9.11 | 4.11 |
| 2005 | 7.56 | 9.93 | 6.1 |
| 2004 | 5.55 | 8.34 | 3.72 |
| 2003 | 5.55 | 7.88 | 3.71 |
| 2002 | 6.75 | 7.81 | 4.99 |
| 2001 | 9.6 | 12.7 | 6.39 |
| 2000 | 13.42 | 17.01 | 6.98 |
| 1999 | 5.44 | 7.41 | 3.73 |
| 1998 | 3.24 | 3.86 | 2.5 |
| 1997 | 3 | 4.28 | 2.15 |