| Year | Value (SE) |
|---|---|
| 2002 | 0.5506 (0.1798) |
| 2004 | 0.7623 (0.7912) |
| 2005 | 0.3545 (0.3503) |
| 2007 | 1.0141 (0.3613) |
| 2008 | 0.9074 (0.2711) |
| 2009 | 1.5220 (0.6096) |
| 2010 | 0.5982 (0.1247) |
| 2011 | 0.5766 (0.0629) |
| 2012 | 0.5923 (0.0479) |
| 2013 | 0.5772 (0.0781) |
| 2014 | 0.6172 (0.0810) |
| 2015 | 0.6332 (0.4103) |
