| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2025 | 0.95 | 1.05 | 0.84 |
| 2024 | 0.8 | 1.21 | 0.66 |
| 2023 | 0.91 | 1.05 | 0.81 |
| 2022 | 0.84 | 0.98 | 0.75 |
| 2021 | 0.86 | 0.99 | 0.77 |
| 2020 | 1.02 | 1.4 | 0.84 |
| 2019 | 0.97 | 1.25 | 0.82 |
| 2018 | 1.29 | 1.72 | 0.91 |
| 2017 | 1.85 | 2.11 | 1.64 |
| 2016 | 1.89 | 2.34 | 1.67 |
| 2015 | 2.43 | 4.44 | 1.68 |
| 2014 | 1.52 | 2.04 | 1.26 |
| 2013 | 1.75 | 2.36 | 1.38 |
| 2012 | 2.72 | 3.87 | 1.58 |
| 2011 | 5.74 | 8.28 | 3.09 |
| 2010 | 7.47 | 8.87 | 5.94 |
| 2009 | 4.85 | 7.42 | 3.36 |
| 2008 | 4.1 | 6.25 | 2.87 |
| 2007 | 4.35 | 6.19 | 1.79 |
| 2006 | 1.42 | 1.98 | 0.9 |
| 2005 | 1.09 | 1.41 | 0.84 |
| 2004 | 1.45 | 1.91 | 1.18 |
| 2003 | 1.74 | 2.08 | 1.43 |
| 2002 | 2.67 | 2.98 | 2.26 |
| 2001 | 3.34 | 3.94 | 2.43 |
| 2000 | 4.23 | 5.16 | 3.12 |
| 1999 | 3.19 | 4.22 | 2.47 |
| 1998 | 3.49 | 5.34 | 2.11 |
| 1997 | 4.87 | 6.63 | 3.64 |