| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2025 | 0.64 | 0.68 | 0.6 |
| 2024 | 0.53 | 0.75 | 0.48 |
| 2023 | 0.63 | 0.75 | 0.5 |
| 2022 | 0.57 | 0.69 | 0.46 |
| 2021 | 0.62 | 0.76 | 0.47 |
| 2020 | 0.55 | 0.7 | 0.44 |
| 2019 | 0.73 | 0.86 | 0.64 |
| 2018 | 0.88 | 1.11 | 0.68 |
| 2017 | 1.21 | 1.72 | 1.01 |
| 2016 | 1.51 | 1.71 | 1.25 |
| 2015 | 1.48 | 2.27 | 1.01 |
| 2014 | 1.12 | 1.35 | 0.95 |
| 2013 | 1.1 | 1.7 | 0.93 |
| 2012 | 0.92 | 1.16 | 0.65 |
| 2011 | 1.29 | 1.85 | 0.86 |
| 2010 | 2.65 | 4.19 | 1.52 |
| 2009 | 1.83 | 3.07 | 1.15 |
| 2008 | 1.75 | 3.07 | 0.89 |
| 2007 | 2.85 | 5.37 | 1.86 |
| 2006 | 1.91 | 2.32 | 1.46 |
| 2005 | 0.56 | 1.57 | 0.26 |
| 2004 | 0.63 | 1.04 | 0.37 |
| 2003 | 0.55 | 0.69 | 0.4 |
| 2002 | 0.82 | 1.19 | 0.62 |
| 2001 | 1.23 | 1.92 | 0.45 |
| 2000 | 0.35 | 0.49 | 0.22 |
| 1999 | 0.22 | 0.41 | 0.09 |
| 1998 | 0.11 | 0.14 | 0.07 |
| 1997 | 0.2 | 0.3 | 0.11 |