| Year | Value (SE) |
|---|---|
| 2009 | 0.6450 (0.0967) |
| 2010 | 0.5746 (0.0743) |
| 2011 | 0.6377 (0.0497) |
| 2012 | 0.6085 (0.0443) |
| 2013 | 0.5192 (0.0606) |
| 2014 | 0.6892 (0.0968) |
| 2015 | 0.5728 (0.0820) |
| 2016 | 0.4836 (0.0262) |
| 2017 | 0.5386 (0.0359) |
| 2018 | 0.5943 (0.0476) |
| 2019 | 0.6353 (0.0484) |
| 2020 | 0.5835 (0.1325) |
| 2021 | 0.7955 (0.3202) |
| 2022 | 0.5771 (0.2107) |
| 2023 | 0.5372 (0.1124) |
| 2024 | 0.6093 (0.2215) |
