| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2025 | 0.85 | 0.93 | 0.81 |
| 2024 | 0.88 | 1.21 | 0.72 |
| 2023 | 0.99 | 1.26 | 0.79 |
| 2022 | 1.16 | 1.6 | 0.92 |
| 2021 | 1.29 | 1.57 | 1.1 |
| 2020 | 1.55 | 1.9 | 1.35 |
| 2019 | 1.72 | 2.29 | 1.47 |
| 2018 | 1.7 | 2.23 | 1.34 |
| 2017 | 2.31 | 2.52 | 2.09 |
| 2016 | 2.56 | 3.28 | 2 |
| 2015 | 3.56 | 5.04 | 1.82 |
| 2014 | 2.44 | 4.65 | 1.96 |
| 2013 | 2.08 | 3.61 | 1.47 |
| 2012 | 1.56 | 1.99 | 1.31 |
| 2011 | 2.28 | 2.93 | 1.55 |
| 2010 | 2.79 | 3.74 | 2.24 |
| 2009 | 3.59 | 4.6 | 2.14 |
| 2008 | 3.83 | 8.03 | 1.54 |
| 2007 | 5.93 | 7.7 | 3.61 |
| 2006 | 2.51 | 3.97 | 1.83 |
| 2005 | 1.55 | 2.29 | 0.88 |
| 2004 | 2.13 | 3.1 | 1.51 |
| 2003 | 2.86 | 3.69 | 2.14 |
| 2002 | 3.84 | 4.56 | 2.61 |
| 2001 | 4.12 | 4.95 | 3.25 |
| 2000 | 3.58 | 4.22 | 2.96 |
| 1999 | 2.62 | 3.27 | 1.96 |
| 1998 | 2.98 | 4.12 | 2.35 |
| 1997 | 15.47 | 22.49 | 11.36 |