| Year | Value (SE) |
|---|---|
| 2002 | 0.4760 (0.0480) |
| 2003 | 0.7320 (0.0729) |
| 2004 | 0.4930 (0.1092) |
| 2006 | 0.8140 (0.0386) |
| 2008 | 0.8950 (0.0790) |
| 2009 | 0.8530 (0.0572) |
| 2010 | 0.5400 (0.0975) |
| 2011 | 0.9010 (0.0834) |
| 2013 | 0.6560 (0.1064) |
| 2014 | 0.6230 (0.0996) |
| 2016 | 0.8640 (0.0781) |
| 2019 | 0.9400 (0.1494) |
