| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2025 | 0.9 | 0.96 | 0.84 |
| 2024 | 0.87 | 1.14 | 0.72 |
| 2023 | 1.22 | 1.48 | 0.9 |
| 2022 | 1.18 | 1.42 | 0.99 |
| 2021 | 1.68 | 2.43 | 1.31 |
| 2020 | 1.32 | 2.93 | 0.73 |
| 2019 | 0.98 | 1.2 | 0.86 |
| 2018 | 1.11 | 1.47 | 0.84 |
| 2017 | 1.64 | 2.17 | 1.36 |
| 2016 | 1.49 | 1.96 | 1.35 |
| 2015 | 2.14 | 2.73 | 1.49 |
| 2014 | 1.57 | 2.34 | 1.08 |
| 2013 | 1.19 | 1.67 | 0.89 |
| 2012 | 1.59 | 2.18 | 1.04 |
| 2011 | 3.8 | 9.65 | 1.77 |
| 2010 | 3.12 | 3.97 | 2.4 |
| 2009 | 2.38 | 3.28 | 1.65 |
| 2008 | 2.08 | 3.42 | 1.21 |
| 2007 | 3.3 | 5.06 | 2.05 |
| 2006 | 2.13 | 2.95 | 1.67 |
| 2005 | 1.23 | 1.88 | 0.88 |
| 2004 | 8.62 | 37.08 | 0.99 |
| 2003 | 10.78 | 27.96 | 4.32 |
| 2002 | 19.29 | 41.54 | 4.75 |
| 2001 | 37.72 | 45.29 | 26.74 |
| 2000 | 7.7 | 11.31 | 5.41 |
| 1999 | 4.9 | 6.78 | 3.85 |
| 1998 | 2.28 | 2.94 | 1.76 |
| 1997 | 2.16 | 3.16 | 1.7 |