| Year | Value (SE) |
|---|---|
| 2000 | 0.5740 (0.0312) |
| 2002 | 0.6022 (0.0139) |
| 2003 | 0.5675 (0.0190) |
| 2004 | 0.5882 (0.0232) |
| 2005 | 0.6616 (0.0183) |
| 2006 | 0.5560 (0.0111) |
| 2007 | 0.6624 (0.0125) |
| 2008 | 0.5306 (0.0241) |
| 2009 | 0.5387 (0.0207) |
| 2010 | 0.7789 (0.0504) |
| 2011 | 0.5126 (0.0145) |
| 2012 | 0.6360 (0.0192) |
| 2013 | 0.6643 (0.0342) |
| 2014 | 0.6859 (0.0299) |
| 2015 | 0.6064 (0.0675) |
| 2016 | 0.5385 (0.0206) |
| 2017 | 0.2843 (0.0170) |
| 2020 | 0.5827 (0.1376) |
| 2021 | 0.5408 (0.2419) |
| 2022 | 0.4648 (0.1691) |
| 2023 | 0.4895 (0.0549) |
