| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2025 | 0.66 | 0.68 | 0.62 |
| 2024 | 0.62 | 0.78 | 0.52 |
| 2023 | 0.67 | 0.78 | 0.58 |
| 2022 | 0.79 | 0.93 | 0.67 |
| 2021 | 0.85 | 0.98 | 0.72 |
| 2020 | 1.01 | 1.2 | 0.88 |
| 2019 | 1.12 | 1.68 | 0.89 |
| 2018 | 0.95 | 1.17 | 0.7 |
| 2017 | 1.2 | 1.44 | 1.04 |
| 2016 | 1.4 | 1.74 | 1.25 |
| 2015 | 1.8 | 2.57 | 1.16 |
| 2014 | 1.23 | 1.78 | 1.01 |
| 2013 | 1.19 | 1.46 | 0.97 |
| 2012 | 1.16 | 1.37 | 0.99 |
| 2011 | 1.34 | 1.79 | 1.02 |
| 2010 | 1.34 | 1.71 | 0.91 |
| 2009 | 1.38 | 1.98 | 0.81 |
| 2008 | 1.31 | 3.8 | 0.69 |
| 2007 | 3.81 | 6.05 | 2.22 |
| 2006 | 1.55 | 2.24 | 1.06 |
| 2005 | 1.09 | 1.35 | 0.85 |
| 2004 | 1.67 | 2.15 | 1.25 |
| 2003 | 2.07 | 2.54 | 1.53 |
| 2002 | 3.04 | 3.62 | 2.62 |
| 2001 | 4.56 | 5.7 | 3.11 |
| 2000 | 6.1 | 7.36 | 5.36 |
| 1999 | 5.32 | 7.98 | 4.48 |
| 1998 | 6.28 | 8.66 | 3.96 |