| Year | Value (SE) |
|---|---|
| 2003 | 0.7912 (0.0353) |
| 2007 | 0.6189 (0.1254) |
| 2008 | 0.7586 (0.0290) |
| 2009 | 0.9352 (0.0379) |
| 2010 | 0.9079 (0.0992) |
| 2011 | 0.8752 (0.0220) |
| 2012 | 0.8389 (0.0246) |
| 2013 | 0.7558 (0.0757) |
| 2014 | 0.8162 (0.0739) |
| 2015 | 0.7129 (0.1226) |
| 2018 | 0.8224 (0.0467) |
| 2019 | 0.8621 (0.0716) |
| 2020 | 0.7064 (0.2096) |
| 2021 | 0.5676 (0.2016) |
| 2022 | 0.8077 (0.1055) |
| 2023 | 0.9540 (0.1439) |
