| Year | Value (SE) |
|---|---|
| 2007 | 0.8049 (0.1215) |
| 2009 | 0.7764 (0.1585) |
| 2010 | 0.7985 (0.1303) |
| 2011 | 0.9669 (0.1706) |
| 2012 | 0.7961 (0.0812) |
| 2013 | 0.6294 (0.1116) |
| 2014 | 0.6868 (0.0917) |
| 2015 | 0.3897 (0.1870) |
| 2016 | 0.6443 (0.0873) |
| 2018 | 0.7994 (0.1922) |
| 2019 | 0.6076 (0.1350) |
| 2020 | 0.9072 (0.3964) |
| 2021 | 0.8060 (0.9269) |
| 2022 | 0.9607 (1.2611) |
| 2023 | 0.4298 (0.1601) |
