| Year | Value (SE) |
|---|---|
| 2008 | 0.9249 (0.0647) |
| 2009 | 0.9120 (0.0333) |
| 2010 | 0.8313 (0.1633) |
| 2011 | 0.9584 (0.0169) |
| 2013 | 0.9052 (0.1306) |
| 2014 | 0.9415 (0.1171) |
| 2015 | 0.7744 (0.3057) |
| 2016 | 0.9545 (0.0674) |
| 2017 | 0.8572 (0.0384) |
| 2018 | 0.9898 (0.0898) |
| 2019 | 0.9324 (0.0874) |
| 2020 | 1.6162 (0.7948) |
| 2021 | 1.1261 (0.4188) |
| 2023 | 1.0769 (0.2641) |
| 2024 | 0.5790 (0.2306) |
