| Year | Value (SE) |
|---|---|
| 2009 | 0.7865 (0.0471) |
| 2010 | 0.7271 (0.0426) |
| 2011 | 0.8361 (0.0239) |
| 2012 | 0.7731 (0.0152) |
| 2013 | 0.7795 (0.0454) |
| 2014 | 0.6980 (0.0333) |
| 2015 | 0.6928 (0.0566) |
| 2016 | 0.6578 (0.0145) |
| 2017 | 0.7716 (0.0168) |
| 2018 | 0.7839 (0.0158) |
| 2019 | 0.7655 (0.0149) |
| 2020 | 0.6464 (0.0558) |
| 2021 | 0.6258 (0.1124) |
| 2022 | 0.6757 (0.1012) |
| 2023 | 0.7622 (0.0417) |
| 2024 | 0.6339 (0.0744) |
