| Year | Value (SE) |
|---|---|
| 2000 | 0.7257 (0.0756) |
| 2001 | 0.6449 (0.0114) |
| 2002 | 0.7743 (0.0271) |
| 2003 | 0.7469 (0.0499) |
| 2004 | 0.6898 (0.0465) |
| 2005 | 0.8323 (0.0457) |
| 2006 | 0.6870 (0.0343) |
| 2007 | 0.8552 (0.0395) |
| 2008 | 0.7594 (0.0450) |
| 2009 | 0.7870 (0.0503) |
| 2010 | 0.8242 (0.1049) |
| 2011 | 0.7364 (0.0530) |
| 2012 | 0.8222 (0.0405) |
| 2013 | 0.9183 (0.1071) |
| 2014 | 0.7963 (0.0705) |
| 2015 | 0.6938 (0.1288) |
| 2016 | 0.7501 (0.0435) |
| 2019 | 0.7369 (0.1139) |
| 2020 | 0.7868 (0.2444) |
| 2021 | 0.7459 (0.5614) |
| 2022 | 0.6471 (0.3425) |
| 2023 | 0.5948 (0.1003) |
