| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2025 | 1.36 | 1.7 | 1.19 |
| 2024 | 1.13 | 1.68 | 0.78 |
| 2023 | 1.1 | 1.98 | 0.96 |
| 2022 | 1.05 | 1.42 | 0.85 |
| 2021 | 1.04 | 1.31 | 0.89 |
| 2020 | 1.11 | 2.05 | 0.87 |
| 2019 | 1.06 | 1.29 | 0.93 |
| 2018 | 1.16 | 1.49 | 0.98 |
| 2017 | 1.79 | 2.23 | 1.43 |
| 2016 | 2.28 | 2.74 | 1.71 |
| 2015 | 2.98 | 5.57 | 1.72 |
| 2014 | 2.08 | 2.52 | 1.54 |
| 2013 | 1.76 | 2.11 | 1.47 |
| 2012 | 2.06 | 2.5 | 1.64 |
| 2011 | 2.64 | 3.32 | 1.93 |
| 2010 | 3.42 | 4.72 | 2.58 |
| 2009 | 3.02 | 3.88 | 2.05 |
| 2008 | 3.7 | 8.06 | 1.62 |
| 2007 | 6.87 | 9.89 | 3.89 |
| 2006 | 3.14 | 4.39 | 1.65 |
| 2005 | 1.7 | 2.12 | 1.2 |
| 2004 | 2.42 | 3.34 | 1.88 |
| 2003 | 3.15 | 3.86 | 2.29 |
| 2002 | 4.3 | 5.13 | 3.18 |
| 2001 | 5.55 | 6.56 | 3.94 |
| 2000 | 5.46 | 6.62 | 4.33 |
| 1999 | 6.34 | 7.84 | 4.64 |
| 1998 | 7.22 | 9.41 | 4.52 |
| 1997 | 8.46 | 12.7 | 4.21 |