| Year | Value (SE) |
|---|---|
| 2009 | 0.8359 (0.1124) |
| 2010 | 0.7934 (0.2192) |
| 2011 | 0.7710 (0.0550) |
| 2012 | 0.8691 (0.0621) |
| 2013 | 0.8763 (0.1096) |
| 2014 | 0.9260 (0.2057) |
| 2015 | 0.8479 (0.2658) |
| 2016 | 0.7641 (0.0653) |
| 2017 | 0.7229 (0.0872) |
| 2018 | 0.5798 (0.1139) |
| 2019 | 0.7663 (0.1350) |
| 2020 | 1.0312 (0.5408) |
| 2022 | 0.7224 (0.4044) |
| 2023 | 0.5632 (0.1256) |
