| Year | Value (SE) |
|---|---|
| 2002 | 0.9540 (0.0732) |
| 2004 | 0.8700 (0.3083) |
| 2005 | 0.5610 (0.1792) |
| 2007 | 0.6490 (0.1021) |
| 2008 | 1.1030 (0.0986) |
| 2009 | 1.0840 (0.1322) |
| 2010 | 0.9800 (0.1036) |
| 2011 | 0.9170 (0.0236) |
| 2012 | 0.9700 (0.0266) |
| 2013 | 0.9900 (0.0770) |
| 2014 | 0.9820 (0.0713) |
| 2015 | 0.5620 (0.2387) |
