| Year | Value (SE) |
|---|---|
| 2002 | 0.7410 (0.0604) |
| 2004 | 0.9540 (0.1015) |
| 2005 | 0.7820 (0.0960) |
| 2007 | 1.0640 (0.1347) |
| 2008 | 0.9220 (0.0689) |
| 2009 | 0.9400 (0.0716) |
| 2010 | 0.9250 (0.0534) |
| 2011 | 0.9040 (0.0211) |
| 2012 | 0.7950 (0.0139) |
| 2013 | 0.9160 (0.0308) |
| 2014 | 0.9250 (0.0574) |
| 2015 | 2.2080 (0.9297) |
