| Year | Value (SE) |
|---|---|
| 2007 | 0.9757 (0.1385) |
| 2009 | 0.7939 (0.0874) |
| 2010 | 0.9085 (0.1233) |
| 2011 | 0.8648 (0.0637) |
| 2012 | 0.8406 (0.0500) |
| 2013 | 0.8551 (0.0839) |
| 2014 | 0.7490 (0.0578) |
| 2015 | 0.6720 (0.2500) |
| 2016 | 0.7915 (0.0624) |
| 2018 | 0.7301 (0.1188) |
| 2019 | 0.6843 (0.1063) |
| 2020 | 0.7060 (0.2661) |
| 2021 | 0.9939 (1.0637) |
| 2022 | 4.3670 (5.1999) |
| 2023 | 0.4431 (0.1422) |
