| Year | Value (SE) |
|---|---|
| 2002 | 1.2170 (0.3760) |
| 2004 | 0.9410 (0.8885) |
| 2005 | 0.9620 (0.8884) |
| 2007 | 1.6390 (0.5130) |
| 2008 | 1.1710 (0.3259) |
| 2009 | 2.2700 (0.8556) |
| 2010 | 0.8740 (0.1541) |
| 2011 | 0.8850 (0.0931) |
| 2012 | 0.7870 (0.0587) |
| 2013 | 0.8320 (0.0908) |
| 2014 | 0.7810 (0.0803) |
| 2015 | 0.6170 (0.2509) |
