| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2026 | 0.43 | 0.47 | 0.39 |
| 2025 | 0.4 | 0.47 | 0.35 |
| 2024 | 0.37 | 0.43 | 0.29 |
| 2023 | 0.43 | 0.5 | 0.37 |
| 2022 | 0.51 | 0.65 | 0.44 |
| 2021 | 0.48 | 0.66 | 0.38 |
| 2020 | 0.42 | 0.5 | 0.38 |
| 2019 | 0.55 | 0.7 | 0.45 |
| 2018 | 0.72 | 0.96 | 0.54 |
| 2017 | 1.01 | 1.47 | 0.8 |
| 2016 | 0.75 | 0.9 | 0.64 |
| 2015 | 1.12 | 1.72 | 0.75 |
| 2014 | 0.54 | 1 | 0.43 |
| 2013 | 0.54 | 0.71 | 0.45 |
| 2012 | 0.77 | 1.16 | 0.56 |
| 2011 | 0.98 | 1.29 | 0.79 |
| 2010 | 1.55 | 3.49 | 0.87 |
| 2009 | 2.07 | 3.37 | 1.1 |
| 2008 | 2.69 | 6.21 | 1.08 |
| 2007 | 3.51 | 6.71 | 1.55 |
| 2006 | 0.95 | 1.44 | 0.67 |
| 2005 | 0.91 | 1.12 | 0.66 |
| 2004 | 1.24 | 1.62 | 1.01 |
| 2003 | 1.38 | 1.79 | 1.2 |
| 2002 | 1.65 | 1.93 | 1.45 |
| 2001 | 1.94 | 2.29 | 1.55 |
| 2000 | 1.87 | 2.31 | 1.31 |
| 1999 | 1.74 | 2.56 | 1.42 |
| 1998 | 1.84 | 2.34 | 1.42 |