| Year | Value (SE) |
|---|---|
| 2008 | 0.7422 (0.1432) |
| 2009 | 0.8686 (0.0899) |
| 2010 | 0.7430 (0.2175) |
| 2011 | 0.5950 (0.0471) |
| 2012 | 0.7867 (0.0515) |
| 2013 | 0.7128 (0.0770) |
| 2014 | 0.7503 (0.0596) |
| 2015 | 0.9273 (0.2401) |
| 2016 | 0.5280 (0.0628) |
| 2017 | 0.7782 (0.0929) |
| 2018 | 0.5973 (0.1215) |
| 2019 | 0.5376 (0.1321) |
| 2020 | 0.5853 (0.2189) |
| 2021 | 0.5273 (0.6501) |
| 2022 | 0.9646 (0.4178) |
