| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2025 | 1.01 | 1.09 | 0.92 |
| 2024 | 0.93 | 1.26 | 0.76 |
| 2023 | 0.94 | 1.26 | 0.8 |
| 2022 | 0.84 | 0.98 | 0.68 |
| 2021 | 0.95 | 1.35 | 0.81 |
| 2020 | 1.1 | 1.38 | 0.94 |
| 2019 | 1.07 | 1.57 | 0.68 |
| 2018 | 0.82 | 1.21 | 0.49 |
| 2017 | 1.38 | 1.76 | 1.09 |
| 2016 | 2.63 | 6.8 | 1.51 |
| 2015 | 2.03 | 3 | 1.15 |
| 2014 | 1.68 | 2.85 | 1.39 |
| 2013 | 1.67 | 2.41 | 1.24 |
| 2012 | 1.37 | 1.69 | 1.1 |
| 2011 | 2.1 | 2.64 | 1.41 |
| 2010 | 2.35 | 3.06 | 1.8 |
| 2009 | 2.57 | 3.36 | 1.7 |
| 2008 | 2.05 | 3.52 | 1.08 |
| 2007 | 4.84 | 16.77 | 2.29 |
| 2006 | 2.7 | 4.36 | 2 |
| 2005 | 1.81 | 2.76 | 1.37 |
| 2004 | 2.34 | 3.55 | 1.68 |
| 2003 | 3.26 | 4.17 | 2.43 |
| 2002 | 4.42 | 5.09 | 3.21 |
| 2001 | 5.92 | 7.42 | 4.28 |
| 2000 | 9.5 | 15.78 | 3.48 |
| 1999 | 4.77 | 6.27 | 3.82 |
| 1998 | 3.99 | 4.79 | 3.1 |
| 1997 | 2.94 | 4.07 | 2.34 |