| Year | Value (SE) |
|---|---|
| 2008 | 0.7813 (0.0985) |
| 2009 | 0.8828 (0.0438) |
| 2010 | 0.7887 (0.2083) |
| 2011 | 0.8140 (0.0275) |
| 2012 | 0.7939 (0.0276) |
| 2013 | 0.9330 (0.0721) |
| 2014 | 0.9094 (0.0440) |
| 2015 | 0.7885 (0.1369) |
| 2016 | 0.6455 (0.0475) |
| 2017 | 0.8064 (0.0768) |
| 2018 | 0.5485 (0.0796) |
| 2019 | 0.5914 (0.0976) |
| 2020 | 0.7428 (0.2631) |
| 2021 | 0.4746 (0.5635) |
| 2022 | 1.2028 (0.4452) |
