| Year | Value (SE) |
|---|---|
| 2009 | 0.7510 (0.1051) |
| 2010 | 0.7990 (0.0920) |
| 2011 | 0.8910 (0.0648) |
| 2012 | 0.8090 (0.0570) |
| 2013 | 0.6960 (0.0705) |
| 2014 | 0.9540 (0.1270) |
| 2015 | 0.8890 (0.1041) |
| 2016 | 0.8470 (0.0414) |
| 2017 | 0.7950 (0.0503) |
| 2018 | 0.8480 (0.0660) |
| 2019 | 0.9130 (0.0675) |
| 2020 | 0.8540 (0.1796) |
| 2021 | 1.1620 (0.4186) |
| 2022 | 0.5790 (0.1929) |
| 2023 | 0.6930 (0.1405) |
| 2024 | 1.0550 (0.3631) |
