| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2025 | 0.54 | 0.62 | 0.5 |
| 2024 | 0.48 | 0.7 | 0.38 |
| 2023 | 0.5 | 0.62 | 0.45 |
| 2022 | 0.51 | 0.69 | 0.44 |
| 2021 | 0.6 | 0.71 | 0.48 |
| 2020 | 0.73 | 0.86 | 0.64 |
| 2019 | 0.85 | 1.17 | 0.71 |
| 2018 | 0.92 | 1.28 | 0.64 |
| 2017 | 1.72 | 3.07 | 1.2 |
| 2016 | 2.3 | 3.52 | 1.9 |
| 2015 | 1.87 | 3.95 | 1.13 |
| 2014 | 1.47 | 1.8 | 1.27 |
| 2013 | 1.56 | 2.17 | 1.17 |
| 2012 | 1.19 | 1.37 | 1.04 |
| 2011 | 1.44 | 1.72 | 1.1 |
| 2010 | 2.03 | 2.94 | 1.53 |
| 2009 | 2.69 | 3.59 | 1.9 |
| 2008 | 2.97 | 5.71 | 1.41 |
| 2007 | 3.77 | 5.69 | 1.68 |
| 2006 | 1.63 | 1.93 | 1.3 |
| 2005 | 1.65 | 2.04 | 1.43 |
| 2004 | 2.43 | 3.13 | 1.96 |
| 2003 | 2.66 | 2.96 | 2.34 |
| 2002 | 3.2 | 3.48 | 2.88 |
| 2001 | 3.57 | 4.13 | 2.79 |
| 2000 | 3.29 | 4.28 | 2.6 |
| 1999 | 2.98 | 3.58 | 2.46 |
| 1998 | 3.27 | 4.41 | 2.2 |
| 1997 | 5.11 | 7.99 | 2.89 |