| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2026 | 0.74 | 0.78 | 0.72 |
| 2025 | 0.72 | 0.75 | 0.66 |
| 2024 | 0.71 | 0.77 | 0.67 |
| 2023 | 0.83 | 0.97 | 0.7 |
| 2022 | 0.79 | 0.84 | 0.73 |
| 2021 | 0.78 | 0.85 | 0.73 |
| 2020 | 0.87 | 1.03 | 0.7 |
| 2019 | 1.95 | 4.57 | 0.78 |
| 2018 | 2.37 | 4.66 | 1.68 |
| 2017 | 2.36 | 3.21 | 1.9 |
| 2016 | 2.68 | 3.53 | 2.02 |
| 2015 | 2.2 | 3.06 | 1.59 |
| 2014 | 1.68 | 2.14 | 1.19 |
| 2013 | 1.29 | 1.52 | 1.11 |
| 2012 | 1.18 | 1.4 | 1 |
| 2011 | 2.46 | 3.73 | 1.01 |
| 2010 | 2.92 | 3.66 | 2.45 |
| 2009 | 2.09 | 2.94 | 1.45 |
| 2008 | 3.27 | 6.83 | 0.88 |
| 2007 | 4.29 | 7.48 | 2.5 |
| 2006 | 2.67 | 3.3 | 1.79 |
| 2005 | 0.54 | 1.82 | 0.18 |
| 2004 | 0.37 | 0.48 | 0.28 |
| 2003 | 0.43 | 0.52 | 0.35 |
| 2002 | 0.52 | 0.66 | 0.39 |
| 2001 | 0.71 | 1.18 | 0.29 |
| 2000 | 0.26 | 0.33 | 0.18 |
| 1999 | 0.17 | 0.28 | 0.1 |
| 1998 | 0.15 | 0.21 | 0.07 |
| 1997 | 0.35 | 0.51 | 0.19 |