| Year | Value (SE) |
|---|---|
| 2007 | 0.8250 (0.0468) |
| 2009 | 0.9780 (0.1734) |
| 2010 | 0.8790 (0.0838) |
| 2011 | 1.1180 (0.1887) |
| 2012 | 0.9470 (0.0887) |
| 2013 | 0.7360 (0.1149) |
| 2014 | 0.9170 (0.1084) |
| 2015 | 0.5800 (0.1873) |
| 2016 | 0.8140 (0.1005) |
| 2018 | 1.0950 (0.2215) |
| 2019 | 0.8880 (0.1716) |
| 2020 | 1.2850 (0.3297) |
| 2021 | 0.8110 (0.3870) |
| 2022 | 0.2200 (0.2491) |
| 2023 | 0.9700 (0.2669) |
