| Year | Value (SE) |
|---|---|
| 2006 | 0.7760 (0.1098) |
| 2007 | 1.0270 (0.0825) |
| 2008 | 0.8290 (0.1505) |
| 2009 | 0.7440 (0.1067) |
| 2010 | 0.7430 (0.0798) |
| 2011 | 0.6340 (0.0999) |
| 2012 | 0.7790 (0.0589) |
| 2013 | 0.8790 (0.0992) |
| 2014 | 0.9840 (0.1464) |
| 2015 | 0.7370 (0.1563) |
| 2016 | 0.9380 (0.1090) |
| 2017 | 0.8700 (0.1079) |
| 2018 | 0.8080 (0.1083) |
| 2019 | 1.5250 (0.5932) |
| 2020 | 0.8970 (0.1568) |
| 2021 | 0.9830 (0.2178) |
| 2022 | 0.9440 (0.4388) |
| 2023 | 0.9550 (0.1782) |
| 2024 | 0.7130 (0.2245) |
