| Year | Value (SE) |
|---|---|
| 2011 | 0.5680 (0.1150) |
| 2012 | 0.6750 (0.0844) |
| 2013 | 0.6070 (0.0944) |
| 2014 | 0.5520 (0.0787) |
| 2015 | 0.3460 (0.0409) |
| 2016 | 0.5310 (0.0372) |
| 2017 | 0.4900 (0.0356) |
| 2018 | 0.5750 (0.0629) |
| 2019 | 0.4950 (0.0482) |
| 2020 | 0.6020 (0.0650) |
| 2021 | 0.5930 (0.1017) |
| 2022 | 0.4450 (0.0820) |
| 2024 | 0.5900 (0.1172) |
