| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2025 | 0.33 | 0.34 | 0.3 |
| 2024 | 0.36 | 0.41 | 0.31 |
| 2023 | 0.44 | 0.55 | 0.37 |
| 2022 | 0.4 | 0.49 | 0.33 |
| 2021 | 0.36 | 0.41 | 0.32 |
| 2020 | 0.51 | 0.8 | 0.35 |
| 2019 | 0.9 | 1.1 | 0.7 |
| 2018 | 0.97 | 1.08 | 0.85 |
| 2017 | 1.03 | 1.18 | 0.93 |
| 2016 | 1.2 | 1.4 | 1.12 |
| 2015 | 1.29 | 1.59 | 1.04 |
| 2014 | 1.32 | 1.57 | 1.15 |
| 2013 | 1.25 | 1.45 | 1.12 |
| 2012 | 1.07 | 1.2 | 0.95 |
| 2011 | 1.29 | 1.58 | 0.98 |
| 2010 | 1.47 | 1.81 | 1.21 |
| 2009 | 1.38 | 1.71 | 1.1 |
| 2008 | 1.62 | 3.22 | 0.91 |
| 2007 | 2.97 | 4.6 | 1.59 |
| 2006 | 1.55 | 1.81 | 1.39 |
| 2005 | 0.77 | 1.45 | 0.52 |
| 2004 | 0.72 | 0.83 | 0.63 |
| 2003 | 0.6 | 0.74 | 0.48 |
| 2002 | 0.62 | 0.77 | 0.48 |
| 2001 | 0.69 | 1.07 | 0.28 |
| 2000 | 0.83 | 1 | 0.7 |
| 1999 | 0.6 | 1.04 | 0.3 |
| 1998 | 0.44 | 0.58 | 0.26 |