| Year | Value (SE) |
|---|---|
| 2002 | 0.6913 (0.0390) |
| 2007 | 0.7625 (0.0659) |
| 2008 | 0.7988 (0.0367) |
| 2009 | 0.8486 (0.0535) |
| 2010 | 0.8591 (0.0319) |
| 2011 | 0.8462 (0.0299) |
| 2012 | 0.8799 (0.0517) |
| 2013 | 0.7768 (0.0818) |
| 2014 | 0.9140 (0.1079) |
| 2015 | 0.6171 (0.1165) |
| 2018 | 0.7880 (0.0519) |
| 2019 | 0.8893 (0.1043) |
| 2020 | 0.7073 (0.3375) |
| 2021 | 0.5627 (0.3480) |
| 2022 | 0.7629 (0.1005) |
| 2023 | 0.7707 (0.1560) |
| 2024 | 0.6032 (0.2050) |
