| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2026 | 0.5 | 0.53 | 0.47 |
| 2025 | 0.56 | 0.69 | 0.48 |
| 2024 | 0.51 | 0.75 | 0.39 |
| 2023 | 0.27 | 0.7 | 0.07 |
| 2022 | 0.64 | 0.72 | 0.56 |
| 2021 | 0.71 | 0.8 | 0.56 |
| 2020 | 0.81 | 1.02 | 0.69 |
| 2019 | 1.1 | 1.28 | 0.93 |
| 2018 | 1.19 | 1.39 | 1.06 |
| 2017 | 1.58 | 1.83 | 1.35 |
| 2016 | 2 | 2.59 | 1.67 |
| 2015 | 2.14 | 3.45 | 1.12 |
| 2014 | 1.44 | 1.95 | 1.31 |
| 2013 | 1.32 | 1.53 | 1.13 |
| 2012 | 1.25 | 1.41 | 1.05 |
| 2011 | 1.61 | 2 | 1.23 |
| 2010 | 2.03 | 2.49 | 1.58 |
| 2009 | 1.93 | 2.43 | 1.4 |
| 2008 | 2.25 | 4.76 | 1.15 |
| 2007 | 3.87 | 5.7 | 2.08 |
| 2006 | 1.55 | 2.14 | 1.28 |
| 2005 | 0.29 | 1.42 | 0.04 |
| 2004 | 0.05 | 0.06 | 0.04 |
| 2003 | 0.06 | 0.07 | 0.05 |
| 2002 | 0.07 | 0.08 | 0.05 |
| 2001 | 0.07 | 0.12 | 0.03 |
| 2000 | 0.02 | 0.04 | 0.01 |
| 1999 | 0.01 | 0.02 | 0.01 |
| 1998 | 0.01 | 0.02 | 0.01 |
| 1997 | 0.02 | 0.03 | 0.01 |