| Year | Value (SE) |
|---|---|
| 2008 | 0.3690 (0.0450) |
| 2009 | 0.5650 (0.0566) |
| 2011 | 0.3960 (0.0322) |
| 2012 | 0.6040 (0.0884) |
| 2013 | 0.4270 (0.0537) |
| 2014 | 0.5200 (0.0693) |
| 2015 | 0.7760 (0.3140) |
| 2016 | 0.4870 (0.0416) |
| 2018 | 0.4340 (0.0397) |
| 2019 | 0.5680 (0.0522) |
| 2020 | 0.5360 (0.0629) |
| 2021 | 0.5750 (0.1492) |
| 2022 | 0.6230 (0.1969) |
| 2023 | 0.4870 (0.0777) |
