| Year | Value (SE) |
|---|---|
| 2002 | 0.6150 (0.0866) |
| 2007 | 0.7995 (0.1009) |
| 2008 | 0.7299 (0.0537) |
| 2009 | 0.6252 (0.0590) |
| 2010 | 0.8287 (0.0472) |
| 2011 | 0.9142 (0.0926) |
| 2012 | 0.9270 (0.0826) |
| 2013 | 0.6566 (0.1160) |
| 2014 | 0.9579 (0.2146) |
| 2015 | 0.7188 (0.1804) |
| 2018 | 0.8172 (0.0706) |
| 2019 | 0.7214 (0.1059) |
| 2020 | 0.5746 (0.2157) |
| 2021 | 0.1769 (0.1063) |
| 2022 | 0.8615 (0.1634) |
| 2023 | 0.6066 (0.1395) |
| 2024 | 0.5063 (0.1672) |
