| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2026 | 1.24 | 1.37 | 1 |
| 2025 | 1.26 | 1.54 | 1.06 |
| 2024 | 1.15 | 1.48 | 0.75 |
| 2023 | 0.84 | 0.99 | 0.74 |
| 2022 | 0.83 | 1.22 | 0.6 |
| 2021 | 1.07 | 1.37 | 0.88 |
| 2020 | 0.98 | 1.1 | 0.87 |
| 2019 | 1.02 | 1.34 | 0.9 |
| 2018 | 1.18 | 1.53 | 0.84 |
| 2017 | 1.07 | 1.2 | 0.94 |
| 2016 | 0.88 | 1.06 | 0.75 |
| 2015 | 1.34 | 2.04 | 0.89 |
| 2014 | 0.81 | 1.58 | 0.67 |
| 2013 | 0.93 | 1.31 | 0.73 |
| 2012 | 1.36 | 1.8 | 0.95 |
| 2011 | 2.92 | 6.32 | 1.37 |
| 2010 | 3.52 | 5.08 | 2.6 |
| 2009 | 3.18 | 4.56 | 1.76 |
| 2008 | 4.44 | 9.64 | 1.37 |
| 2007 | 6.67 | 10.25 | 4.26 |
| 2006 | 2.22 | 4.5 | 1.55 |
| 2005 | 1.35 | 1.69 | 0.93 |
| 2004 | 2.97 | 4.65 | 1.59 |
| 2003 | 4.13 | 4.93 | 3.3 |
| 2002 | 3.38 | 4.2 | 1.98 |
| 2001 | 3.81 | 4.77 | 2.8 |
| 2000 | 3.36 | 4.64 | 2.16 |
| 1999 | 2.29 | 3.17 | 1.69 |
| 1998 | 2.28 | 2.93 | 1.81 |
| 1997 | 2.82 | 3.6 | 2.17 |