| Year | Value (SE) |
|---|---|
| 2008 | 0.8590 (0.1055) |
| 2009 | 0.8790 (0.0416) |
| 2011 | 0.9530 (0.0248) |
| 2012 | 0.9630 (0.0430) |
| 2013 | 0.9370 (0.1130) |
| 2014 | 0.9610 (0.0824) |
| 2015 | 1.5120 (0.4050) |
| 2016 | 0.7640 (0.0485) |
| 2018 | 1.0570 (0.0690) |
| 2019 | 0.9570 (0.0362) |
| 2020 | 0.9750 (0.2188) |
| 2021 | 2.3770 (1.3236) |
| 2022 | 1.3350 (0.3829) |
| 2023 | 1.2820 (0.3740) |
