| Year | Value (SE) |
|---|---|
| 2008 | 0.6250 (0.0445) |
| 2009 | 0.7270 (0.0543) |
| 2010 | 0.7460 (0.0495) |
| 2011 | 0.6800 (0.0326) |
| 2013 | 0.3630 (0.0393) |
| 2014 | 0.6770 (0.0927) |
| 2015 | 0.4560 (0.1426) |
| 2016 | 0.4790 (0.0376) |
| 2017 | 0.5570 (0.0354) |
| 2018 | 0.5770 (0.0595) |
| 2019 | 0.9980 (0.1939) |
| 2020 | 0.5060 (0.0846) |
| 2021 | 0.3840 (0.0718) |
| 2023 | 0.6790 (0.1403) |
| 2024 | 0.5600 (0.2623) |
