| Year | Value (SE) |
|---|---|
| 2002 | 0.7431 (0.2373) |
| 2004 | 0.7990 (0.8318) |
| 2005 | 0.4533 (0.4505) |
| 2007 | 0.9531 (0.3342) |
| 2008 | 0.9842 (0.2882) |
| 2009 | 1.6191 (0.6440) |
| 2010 | 0.6467 (0.1331) |
| 2011 | 0.6379 (0.0692) |
| 2012 | 0.7451 (0.0596) |
| 2013 | 0.6301 (0.0851) |
| 2014 | 0.6672 (0.0846) |
| 2015 | 0.2868 (0.1687) |
