| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2025 | 0.69 | 0.74 | 0.66 |
| 2024 | 0.69 | 0.78 | 0.6 |
| 2023 | 0.69 | 0.82 | 0.63 |
| 2022 | 0.68 | 0.8 | 0.63 |
| 2021 | 0.68 | 0.77 | 0.64 |
| 2020 | 0.69 | 0.79 | 0.65 |
| 2019 | 0.81 | 1 | 0.73 |
| 2018 | 0.9 | 1.18 | 0.72 |
| 2017 | 1.3 | 2.01 | 1.09 |
| 2016 | 1.09 | 1.25 | 0.96 |
| 2015 | 1.85 | 2.77 | 1.07 |
| 2014 | 1.31 | 2.73 | 0.98 |
| 2013 | 0.92 | 1.33 | 0.68 |
| 2012 | 0.92 | 1.05 | 0.77 |
| 2011 | 1.24 | 1.5 | 0.93 |
| 2010 | 1.69 | 2.38 | 1.33 |
| 2009 | 2.16 | 2.77 | 1.67 |
| 2008 | 4.82 | 9.12 | 1.55 |
| 2007 | 7.22 | 10.78 | 3.14 |
| 2006 | 2.6 | 3.34 | 1.95 |
| 2005 | 3.13 | 3.82 | 1.99 |
| 2004 | 3.56 | 4.87 | 1.75 |
| 2003 | 4.32 | 5.14 | 3.33 |
| 2002 | 4.1 | 4.87 | 3.25 |
| 2001 | 4.94 | 5.76 | 3.89 |
| 2000 | 3.11 | 3.91 | 2.45 |
| 1999 | 2.75 | 3.48 | 2.36 |
| 1998 | 3.77 | 4.93 | 1.73 |
| 1997 | 9.77 | 14.52 | 6.87 |