| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2026 | 0.87 | 0.91 | 0.76 |
| 2025 | 0.84 | 0.91 | 0.78 |
| 2024 | 0.98 | 1.25 | 0.77 |
| 2023 | 1.08 | 1.32 | 0.9 |
| 2022 | 0.88 | 1.02 | 0.69 |
| 2021 | 1.15 | 1.68 | 0.81 |
| 2020 | 1.05 | 1.41 | 0.82 |
| 2019 | 0.97 | 1.32 | 0.76 |
| 2018 | 0.85 | 1.04 | 0.72 |
| 2017 | 1.2 | 1.45 | 1 |
| 2016 | 1.21 | 1.39 | 0.99 |
| 2015 | 1.65 | 3.16 | 1.07 |
| 2014 | 1.22 | 1.84 | 0.99 |
| 2013 | 1.08 | 1.21 | 0.92 |
| 2012 | 1.15 | 1.34 | 0.95 |
| 2011 | 1.63 | 2.51 | 1.08 |
| 2010 | 2.37 | 3.57 | 1.59 |
| 2009 | 2.22 | 3.59 | 0.95 |
| 2008 | 1.56 | 2.89 | 0.78 |
| 2007 | 1.95 | 2.9 | 1.13 |
| 2006 | 1.1 | 1.29 | 0.96 |
| 2005 | 0.91 | 1.04 | 0.8 |
| 2004 | 1.35 | 1.88 | 0.92 |
| 2003 | 1.76 | 2.21 | 1.38 |
| 2002 | 2.28 | 2.73 | 1.49 |
| 2001 | 3 | 4.16 | 1.99 |
| 2000 | 2.73 | 4.18 | 1.91 |
| 1999 | 2.74 | 3.59 | 2.11 |
| 1998 | 3.79 | 5.11 | 2.6 |
| 1997 | 8.09 | 14.87 | 5.42 |