| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2025 | 0.63 | 0.69 | 0.57 |
| 2024 | 0.55 | 0.81 | 0.45 |
| 2023 | 0.61 | 0.71 | 0.54 |
| 2022 | 0.63 | 1.02 | 0.5 |
| 2021 | 0.55 | 0.61 | 0.5 |
| 2020 | 0.67 | 0.82 | 0.58 |
| 2019 | 0.91 | 1.33 | 0.69 |
| 2018 | 0.97 | 1.38 | 0.65 |
| 2017 | 1.62 | 2.06 | 1.22 |
| 2016 | 2.17 | 2.65 | 1.95 |
| 2015 | 2.55 | 5.92 | 1.61 |
| 2014 | 1.32 | 2.03 | 1.06 |
| 2013 | 1.32 | 1.61 | 1.12 |
| 2012 | 1.7 | 2.23 | 1.28 |
| 2011 | 2.11 | 2.82 | 1.51 |
| 2010 | 2.15 | 2.89 | 1.7 |
| 2009 | 2.19 | 3.58 | 1.16 |
| 2008 | 2.25 | 4.88 | 0.79 |
| 2007 | 3.53 | 5.35 | 1.54 |
| 2006 | 1.4 | 1.81 | 1.17 |
| 2005 | 1.39 | 1.85 | 1.01 |
| 2004 | 1.93 | 2.81 | 1.43 |
| 2003 | 2.63 | 3.05 | 2.08 |
| 2002 | 4.01 | 5.29 | 3.36 |
| 2001 | 6.19 | 7.62 | 4.36 |
| 2000 | 6.84 | 7.93 | 6.09 |
| 1999 | 7.39 | 11.27 | 5.85 |
| 1998 | 10.91 | 16.18 | 7.08 |
| 1997 | 9.25 | 12.83 | 6.31 |