| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2025 | 1.6 | 1.9 | 1.36 |
| 2024 | 1.37 | 2.85 | 0.6 |
| 2023 | 0.78 | 0.88 | 0.72 |
| 2022 | 0.8 | 0.9 | 0.7 |
| 2021 | 0.89 | 0.99 | 0.81 |
| 2020 | 0.98 | 1.1 | 0.88 |
| 2019 | 1.15 | 1.49 | 1.02 |
| 2018 | 1.13 | 1.3 | 0.94 |
| 2017 | 1.45 | 1.72 | 1.25 |
| 2016 | 1.98 | 3.03 | 1.66 |
| 2015 | 3.48 | 6.38 | 1.92 |
| 2014 | 2.02 | 3.35 | 1.56 |
| 2013 | 1.67 | 2.26 | 1.35 |
| 2012 | 1.51 | 1.85 | 1.25 |
| 2011 | 2 | 2.45 | 1.48 |
| 2010 | 3.21 | 5.05 | 2.11 |
| 2009 | 4.18 | 6.33 | 2.32 |
| 2008 | 3.85 | 6.69 | 1.89 |
| 2007 | 5.88 | 9.74 | 2.17 |
| 2006 | 1.66 | 2.2 | 1.23 |
| 2005 | 1 | 1.34 | 0.73 |
| 2004 | 2.35 | 5.61 | 1.09 |
| 2003 | 1.51 | 1.81 | 1.22 |
| 2002 | 2.16 | 2.39 | 1.74 |
| 2001 | 2.65 | 3.19 | 1.94 |
| 2000 | 3.11 | 3.93 | 2.54 |
| 1999 | 2.21 | 3.48 | 1.85 |
| 1998 | 2.72 | 3.31 | 2.29 |
| 1997 | 2.95 | 4.29 | 1.82 |