| Year | Value (SE) |
|---|---|
| 2008 | 0.9160 (0.1455) |
| 2009 | 0.8760 (0.0888) |
| 2010 | 1.0080 (0.0872) |
| 2011 | 0.9960 (0.0763) |
| 2012 | 0.9100 (0.0640) |
| 2013 | 0.8930 (0.0883) |
| 2014 | 0.8170 (0.0637) |
| 2015 | 0.6670 (0.1049) |
| 2016 | 0.7690 (0.0497) |
| 2017 | 0.8230 (0.0765) |
| 2018 | 0.7520 (0.0764) |
| 2019 | 1.3040 (0.1888) |
| 2020 | 0.8150 (0.1712) |
| 2021 | 1.0810 (0.2235) |
| 2022 | 2.0430 (1.0179) |
| 2023 | 0.7420 (0.1446) |
