| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2025 | 0.4 | 0.42 | 0.38 |
| 2024 | 0.45 | 0.52 | 0.36 |
| 2023 | 0.54 | 0.66 | 0.43 |
| 2022 | 0.52 | 0.6 | 0.44 |
| 2021 | 0.53 | 0.68 | 0.46 |
| 2020 | 0.51 | 0.59 | 0.45 |
| 2019 | 0.59 | 0.71 | 0.49 |
| 2018 | 0.69 | 1.14 | 0.46 |
| 2017 | 1.21 | 1.78 | 0.85 |
| 2016 | 1.58 | 1.97 | 1.19 |
| 2015 | 2.43 | 3.72 | 1.43 |
| 2014 | 1.59 | 3.35 | 1.09 |
| 2013 | 1.23 | 1.53 | 1.01 |
| 2012 | 1.32 | 1.85 | 1.04 |
| 2011 | 1.67 | 2.17 | 1.11 |
| 2010 | 2.3 | 3.36 | 1.78 |
| 2009 | 2.32 | 3.27 | 1.53 |
| 2008 | 2.96 | 5.89 | 1.19 |
| 2007 | 6.42 | 10.4 | 2.93 |
| 2006 | 2.28 | 3.07 | 1.62 |
| 2005 | 1.57 | 2.03 | 1.12 |
| 2004 | 2.13 | 2.84 | 1.25 |
| 2003 | 2.21 | 2.67 | 1.8 |
| 2002 | 3.23 | 3.57 | 2.71 |
| 2001 | 4 | 4.61 | 2.86 |
| 2000 | 3.38 | 3.82 | 2.84 |
| 1999 | 3.09 | 3.96 | 2.31 |
| 1998 | 6.19 | 8.34 | 4.71 |
| 1997 | 6.64 | 8.52 | 4.31 |