| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2025 | 0.9 | 1.02 | 0.84 |
| 2024 | 0.97 | 1.13 | 0.73 |
| 2023 | 1.09 | 1.4 | 0.91 |
| 2022 | 1.44 | 1.87 | 1.03 |
| 2021 | 1.79 | 2.41 | 1.27 |
| 2020 | 2.53 | 2.85 | 1.94 |
| 2019 | 2.2 | 2.82 | 1.58 |
| 2018 | 1.97 | 2.59 | 1.64 |
| 2017 | 1.66 | 2.24 | 1.15 |
| 2016 | 1.15 | 1.42 | 0.89 |
| 2015 | 1.53 | 2.29 | 1.11 |
| 2014 | 1.26 | 1.71 | 1.12 |
| 2013 | 1.6 | 2.23 | 1.2 |
| 2012 | 1.74 | 2.63 | 1.23 |
| 2011 | 3.33 | 4.57 | 1.91 |
| 2010 | 1.89 | 2.85 | 1.38 |
| 2009 | 2.19 | 2.66 | 1.64 |
| 2008 | 3.41 | 9.66 | 0.97 |
| 2007 | 5.2 | 8.74 | 2.27 |
| 2006 | 1.66 | 2.33 | 1.33 |
| 2005 | 0.78 | 1.33 | 0.4 |
| 2004 | 1.32 | 2.08 | 0.92 |
| 2003 | 1.78 | 2.08 | 1.52 |
| 2002 | 2.28 | 2.57 | 1.65 |
| 2001 | 2.49 | 3.05 | 1.69 |
| 2000 | 2.06 | 2.85 | 1.39 |
| 1999 | 1.68 | 2.08 | 1.35 |
| 1998 | 1.89 | 2.31 | 1.4 |
| 1997 | 1.95 | 3.06 | 1.42 |