| Year | Value (SE) |
|---|---|
| 2008 | 0.5856 (0.0323) |
| 2009 | 0.8462 (0.0228) |
| 2011 | 0.6649 (0.0111) |
| 2012 | 0.6242 (0.0176) |
| 2013 | 0.6324 (0.0329) |
| 2014 | 0.7544 (0.0356) |
| 2015 | 0.7227 (0.0784) |
| 2016 | 0.8324 (0.0366) |
| 2018 | 0.7277 (0.0255) |
| 2019 | 0.7874 (0.0175) |
| 2020 | 0.7728 (0.0588) |
| 2021 | 0.6175 (0.0899) |
| 2022 | 0.5285 (0.0562) |
| 2023 | 0.8644 (0.0939) |
