| Year | Value (SE) |
|---|---|
| 2002 | 0.4270 (0.0722) |
| 2003 | 0.5530 (0.0798) |
| 2004 | 0.4510 (0.3032) |
| 2006 | 0.6530 (0.0490) |
| 2008 | 0.9210 (0.0993) |
| 2009 | 0.8410 (0.0966) |
| 2010 | 0.6120 (0.0802) |
| 2011 | 0.9580 (0.1328) |
| 2013 | 0.6800 (0.1426) |
| 2014 | 0.6390 (0.1145) |
| 2016 | 0.4820 (0.0545) |
| 2019 | 0.7400 (0.1050) |
