| 时间 | 平均 | 最高 | 最低 |
|---|---|---|---|
| 2025 | 0.6 | 0.66 | 0.56 |
| 2024 | 0.52 | 0.59 | 0.46 |
| 2023 | 0.44 | 0.5 | 0.39 |
| 2022 | 0.41 | 0.44 | 0.37 |
| 2021 | 0.45 | 0.5 | 0.41 |
| 2020 | 0.52 | 0.59 | 0.47 |
| 2019 | 0.64 | 0.74 | 0.57 |
| 2018 | 0.74 | 0.95 | 0.66 |
| 2017 | 0.78 | 0.88 | 0.72 |
| 2016 | 0.75 | 0.91 | 0.69 |
| 2015 | 1.09 | 1.43 | 0.84 |
| 2014 | 0.8 | 1.19 | 0.73 |
| 2013 | 0.94 | 1.14 | 0.82 |
| 2012 | 1.08 | 1.24 | 0.95 |
| 2011 | 1.35 | 1.68 | 1.15 |
| 2010 | 1.8 | 2.22 | 1.52 |
| 2009 | 2.05 | 2.5 | 1.63 |
| 2008 | 2.53 | 4.17 | 1.66 |
| 2007 | 3.77 | 4.55 | 3.09 |