| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2026 | 2.72 | 2.95 | 2.39 |
| 2025 | 2.25 | 2.91 | 1.85 |
| 2024 | 1.98 | 2.73 | 1.59 |
| 2023 | 2.65 | 3.34 | 2.24 |
| 2022 | 2.17 | 3.46 | 1.54 |
| 2021 | 1.48 | 2.01 | 0.96 |
| 2020 | 1.32 | 1.81 | 0.93 |
| 2019 | 1.14 | 1.31 | 0.9 |
| 2018 | 1.14 | 1.57 | 0.85 |
| 2017 | 1.94 | 2.77 | 1.48 |
| 2016 | 2.93 | 6.03 | 1.98 |
| 2015 | 4.39 | 8.29 | 2.49 |
| 2014 | 2.76 | 3.22 | 2.11 |
| 2013 | 2.6 | 4.66 | 1.86 |
| 2012 | 2.15 | 2.62 | 1.64 |
| 2011 | 3.14 | 4.27 | 1.95 |
| 2010 | 4.17 | 5.31 | 3.49 |
| 2009 | 3.14 | 4.07 | 1.71 |
| 2008 | 4.94 | 11.86 | 1.39 |
| 2007 | 9.1 | 13.78 | 4.34 |
| 2006 | 2.45 | 4.66 | 1.01 |
| 2005 | 1.25 | 1.67 | 0.88 |
| 2004 | 2.07 | 2.74 | 1.54 |
| 2003 | 2.88 | 3.61 | 2.08 |
| 2002 | 3.83 | 4.41 | 3.29 |
| 2001 | 5.05 | 5.91 | 3.99 |
| 2000 | 5.25 | 6.43 | 3.84 |
| 1999 | 4.43 | 6.06 | 3.64 |
| 1998 | 6.63 | 9.56 | 4.72 |
| 1997 | 8.05 | 12.74 | 5.72 |