| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2025 | 0.75 | 0.86 | 0.63 |
| 2024 | 0.95 | 1.3 | 0.66 |
| 2023 | 1.5 | 1.95 | 1.18 |
| 2022 | 2.92 | 4.3 | 1.68 |
| 2021 | 3.17 | 5.52 | 1.7 |
| 2020 | 1.53 | 2.71 | 1 |
| 2019 | 1.23 | 1.73 | 0.96 |
| 2018 | 1.92 | 2.49 | 1.34 |
| 2017 | 2.33 | 3.32 | 1.67 |
| 2016 | 2.49 | 4.34 | 1.88 |
| 2015 | 2.61 | 3.84 | 1.6 |
| 2014 | 2.12 | 2.62 | 1.47 |
| 2013 | 1.6 | 2.03 | 1.29 |
| 2012 | 1.63 | 2.1 | 1.08 |
| 2011 | 2.34 | 3.26 | 1.68 |
| 2010 | 2.6 | 3.52 | 1.78 |
| 2009 | 2.93 | 4.16 | 1.36 |
| 2008 | 2.55 | 5.27 | 1.04 |
| 2007 | 4.24 | 6.98 | 1.65 |
| 2006 | 1.4 | 2 | 1.07 |
| 2005 | 1.15 | 1.52 | 0.81 |
| 2004 | 1.84 | 2.45 | 1.47 |
| 2003 | 1.86 | 2.11 | 1.6 |
| 2002 | 2.69 | 4.21 | 1.87 |
| 2001 | 4.06 | 4.57 | 3 |
| 2000 | 4.49 | 5.19 | 4.1 |
| 1999 | 4.51 | 6.06 | 3.61 |
| 1998 | 6.12 | 8.7 | 4.59 |
| 1997 | 6.28 | 7.88 | 4.11 |