| Year | Value (SE) |
|---|---|
| 2003 | 0.6443 (0.1609) |
| 2007 | 0.8829 (0.2985) |
| 2008 | 0.5914 (0.0456) |
| 2009 | 0.9078 (0.1071) |
| 2010 | 0.8218 (0.1083) |
| 2011 | 0.7325 (0.0631) |
| 2012 | 0.8411 (0.0816) |
| 2013 | 0.6842 (0.1517) |
| 2014 | 0.8992 (0.2313) |
| 2015 | 0.3219 (0.0916) |
| 2018 | 0.6044 (0.0532) |
| 2019 | 0.6441 (0.0962) |
| 2020 | 1.0308 (0.4865) |
| 2021 | 0.3016 (0.1239) |
| 2022 | 0.5232 (0.1762) |
| 2023 | 0.5068 (0.1195) |
