| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2025 | 0.86 | 1.07 | 0.78 |
| 2024 | 0.93 | 1.14 | 0.74 |
| 2023 | 0.81 | 0.9 | 0.72 |
| 2022 | 0.95 | 1.2 | 0.75 |
| 2021 | 1.31 | 1.66 | 1.1 |
| 2020 | 0.87 | 1.47 | 0.63 |
| 2019 | 1.02 | 1.38 | 0.82 |
| 2018 | 1.35 | 2.24 | 0.94 |
| 2017 | 1.79 | 2.23 | 1.47 |
| 2016 | 1.57 | 2.26 | 1.39 |
| 2015 | 2.58 | 3.88 | 1.8 |
| 2014 | 1.97 | 2.88 | 1.55 |
| 2013 | 1.71 | 2.02 | 1.3 |
| 2012 | 1.8 | 2.36 | 1.28 |
| 2011 | 3.17 | 4.89 | 1.75 |
| 2010 | 2.74 | 4.08 | 2.03 |
| 2009 | 1.96 | 2.72 | 1.16 |
| 2008 | 2.39 | 5.33 | 1.11 |
| 2007 | 5.37 | 6.81 | 3.79 |
| 2006 | 2.64 | 4.02 | 1.87 |
| 2005 | 1.54 | 2.71 | 0.86 |
| 2004 | 2.28 | 3.64 | 1.62 |
| 2003 | 2.12 | 3.35 | 1.67 |
| 2002 | 2.53 | 3.65 | 1.93 |
| 2001 | 3.54 | 4.12 | 2.86 |
| 2000 | 3.49 | 5.16 | 2.71 |
| 1999 | 2.88 | 4.22 | 2.19 |
| 1998 | 3.22 | 4.3 | 2.15 |
| 1997 | 5.52 | 8.3 | 3.89 |