| Year | Value (SE) |
|---|---|
| 2008 | 0.7081 (0.1054) |
| 2009 | 0.8024 (0.0710) |
| 2010 | 0.7471 (0.1294) |
| 2011 | 0.7430 (0.0336) |
| 2012 | 0.7140 (0.0302) |
| 2013 | 0.9042 (0.0895) |
| 2014 | 0.9121 (0.0971) |
| 2015 | 0.6940 (0.1524) |
| 2016 | 0.7660 (0.0660) |
| 2018 | 0.6996 (0.0898) |
| 2019 | 0.8122 (0.0729) |
| 2020 | 0.5709 (0.2046) |
| 2022 | 0.5492 (0.1683) |
| 2023 | 0.7226 (0.1140) |
| 2025 | 0.3887 (0.1844) |
