| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2025 | 0.49 | 0.51 | 0.47 |
| 2024 | 0.55 | 0.61 | 0.49 |
| 2023 | 0.27 | 0.59 | 0.08 |
| 2022 | 0.58 | 0.62 | 0.54 |
| 2021 | 0.64 | 0.7 | 0.55 |
| 2020 | 0.74 | 0.85 | 0.67 |
| 2019 | 0.95 | 1.16 | 0.73 |
| 2018 | 1.04 | 1.14 | 0.95 |
| 2017 | 1.25 | 1.37 | 1.11 |
| 2016 | 1.39 | 1.6 | 1.23 |
| 2015 | 1.64 | 2.11 | 1.1 |
| 2014 | 1.32 | 2.08 | 1.16 |
| 2013 | 1.32 | 1.54 | 1.14 |
| 2012 | 0.97 | 1.27 | 0.88 |
| 2011 | 1.31 | 1.62 | 0.88 |
| 2010 | 1.52 | 1.83 | 1.24 |
| 2009 | 1.5 | 1.96 | 0.93 |
| 2008 | 1.91 | 4.4 | 0.74 |
| 2007 | 3.67 | 4.71 | 2.49 |
| 2006 | 1.79 | 2.62 | 1.13 |
| 2005 | 0.23 | 1.11 | 0.03 |
| 2004 | 0.06 | 0.08 | 0.04 |
| 2003 | 0.08 | 0.09 | 0.06 |
| 2002 | 0.11 | 0.12 | 0.08 |
| 2001 | 0.11 | 0.15 | 0.06 |
| 2000 | 0.04 | 0.06 | 0.02 |
| 1999 | 0.02 | 0.04 | 0.01 |
| 1998 | 0.03 | 0.04 | 0.02 |
| 1997 | 0.22 | 0.32 | 0.16 |